diff --git a/.gitignore b/.gitignore
index eaf169cb8..c8aa69a4d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,25 +1,13 @@
 Thumbs.db
 /.app_is_ready
-/deploy.exclude
-/deploy.sh
 /messages.mo
 /node_modules
+/locale/**/*.po~
 /package-lock.json
-*~
-*.DS_Store
-#*
-.idea/*
-plugins.local/*
-themes.local/*
-config.php
-feed-icons/*
-cache/*/*
-lock/*
-tags
-cache/htmlpurifier/*/*ser
-lib/htmlpurifier/library/HTMLPurifier/DefinitionCache/Serializer/*/*ser
-web.config
-/.save.cson
-/.tags*
-/.gutentags
+/plugins.local/*
+/themes.local/*
+/config.php
+/feed-icons/*
+/cache/*/*
+/lock/*
 /.vscode/settings.json
diff --git a/api/index.php b/api/index.php
index 6b0071141..d1e02bbd4 100644
--- a/api/index.php
+++ b/api/index.php
@@ -1,8 +1,6 @@
 <?php
 	error_reporting(E_ERROR | E_PARSE);
 
-	require_once "../config.php";
-
 	set_include_path(__DIR__ . PATH_SEPARATOR .
 		dirname(__DIR__) . PATH_SEPARATOR .
 		dirname(__DIR__) . "/include" . PATH_SEPARATOR .
@@ -14,7 +12,6 @@
 	define('NO_SESSION_AUTOSTART', true);
 
 	require_once "autoload.php";
-	require_once "db-prefs.php";
 	require_once "functions.php";
 	require_once "sessions.php";
 
diff --git a/backend.php b/backend.php
index b6b3e0030..9bc1449d0 100644
--- a/backend.php
+++ b/backend.php
@@ -26,8 +26,6 @@
 	require_once "autoload.php";
 	require_once "sessions.php";
 	require_once "functions.php";
-	require_once "config.php";
-	require_once "db-prefs.php";
 
 	$op = (string)clean($op);
 	$method = (string)clean($method);
@@ -40,7 +38,7 @@
 
 	header("Content-Type: text/json; charset=utf-8");
 
-	if (SINGLE_USER_MODE) {
+	if (Config::get(Config::SINGLE_USER_MODE)) {
 		UserHelper::authenticate( "admin", null);
 	}
 
diff --git a/classes/api.php b/classes/api.php
index 5677cb908..6f3ee77db 100755
--- a/classes/api.php
+++ b/classes/api.php
@@ -57,7 +57,7 @@ class API extends Handler {
 		$password = clean($_REQUEST["password"]);
 		$password_base64 = base64_decode(clean($_REQUEST["password"]));
 
-		if (SINGLE_USER_MODE) $login = "admin";
+		if (Config::get(Config::SINGLE_USER_MODE)) $login = "admin";
 
 		if ($uid = UserHelper::find_user_by_login($login)) {
 			if (get_pref("ENABLE_API_ACCESS", $uid)) {
@@ -361,9 +361,10 @@ class API extends Handler {
 	}
 
 	function getConfig() {
-		$config = array(
-			"icons_dir" => ICONS_DIR,
-			"icons_url" => ICONS_URL);
+		$config = [
+			"icons_dir" => Config::get(Config::ICONS_DIR),
+			"icons_url" => Config::get(Config::ICONS_URL)
+		];
 
 		$config["daemon_is_running"] = file_is_locked("update_daemon.lock");
 
diff --git a/classes/article.php b/classes/article.php
index acd83694c..a2a38118b 100755
--- a/classes/article.php
+++ b/classes/article.php
@@ -85,7 +85,7 @@ class Article extends Handler_Protected {
 					content = ?, content_hash = ? WHERE id = ?");
 				$sth->execute([$content, $content_hash, $ref_id]);
 
-				if (DB_TYPE == "pgsql"){
+				if (Config::get(Config::DB_TYPE) == "pgsql") {
 					$sth = $pdo->prepare("UPDATE ttrss_entries
 					SET tsvector_combined = to_tsvector( :ts_content)
 					WHERE id = :id");
@@ -130,7 +130,7 @@ class Article extends Handler_Protected {
 
 			if ($row = $sth->fetch()) {
 				$ref_id = $row["id"];
-				if (DB_TYPE == "pgsql"){
+				if (Config::get(Config::DB_TYPE) == "pgsql"){
 					$sth = $pdo->prepare("UPDATE ttrss_entries
 					SET tsvector_combined = to_tsvector( :ts_content)
 					WHERE id = :id");
@@ -475,7 +475,7 @@ class Article extends Handler_Protected {
 
         // purge orphaned posts in main content table
 
-        if (DB_TYPE == "mysql")
+        if (Config::get(Config::DB_TYPE) == "mysql")
             $limit_qpart = "LIMIT 5000";
         else
             $limit_qpart = "";
diff --git a/classes/config.php b/classes/config.php
new file mode 100644
index 000000000..6f62863e9
--- /dev/null
+++ b/classes/config.php
@@ -0,0 +1,142 @@
+<?php
+class Config {
+	private const _ENVVAR_PREFIX = "TTRSS_";
+
+	// override defaults, defined below in _DEFAULTS[], via environment: DB_TYPE becomes TTRSS_DB_TYPE, etc
+
+	const DB_TYPE = "DB_TYPE";
+	const DB_HOST = "DB_HOST";
+	const DB_USER = "DB_USER";
+	const DB_NAME = "DB_NAME";
+	const DB_PASS = "DB_PASS";
+	const DB_PORT = "DB_PORT";
+	const MYSQL_CHARSET = "MYSQL_CHARSET";
+	const SELF_URL_PATH = "SELF_URL_PATH";
+	const SINGLE_USER_MODE = "SINGLE_USER_MODE";
+	const SIMPLE_UPDATE_MODE = "SIMPLE_UPDATE_MODE";
+	const PHP_EXECUTABLE = "PHP_EXECUTABLE";
+	const LOCK_DIRECTORY = "LOCK_DIRECTORY";
+	const CACHE_DIR = "CACHE_DIR";
+	const ICONS_DIR = "ICONS_DIR";
+	const ICONS_URL = "ICONS_URL";
+	const AUTH_AUTO_CREATE = "AUTH_AUTO_CREATE";
+	const AUTH_AUTO_LOGIN = "AUTH_AUTO_LOGIN";
+	const FORCE_ARTICLE_PURGE = "FORCE_ARTICLE_PURGE";
+	const ENABLE_REGISTRATION = "ENABLE_REGISTRATION";
+	const SESSION_COOKIE_LIFETIME = "SESSION_COOKIE_LIFETIME";
+	const SMTP_FROM_NAME = "SMTP_FROM_NAME";
+	const SMTP_FROM_ADDRESS = "SMTP_FROM_ADDRESS";
+	const DIGEST_SUBJECT = "DIGEST_SUBJECT";
+	const CHECK_FOR_UPDATES = "CHECK_FOR_UPDATES";
+	const PLUGINS = "PLUGINS";
+	const LOG_DESTINATION = "LOG_DESTINATION";
+	const LOCAL_OVERRIDE_STYLESHEET = "LOCAL_OVERRIDE_STYLESHEET";
+	const DAEMON_MAX_CHILD_RUNTIME = "DAEMON_MAX_CHILD_RUNTIME";
+	const DAEMON_MAX_JOBS = "DAEMON_MAX_JOBS";
+	const FEED_FETCH_TIMEOUT = "FEED_FETCH_TIMEOUT";
+	const FEED_FETCH_NO_CACHE_TIMEOUT = "FEED_FETCH_NO_CACHE_TIMEOUT";
+	const FILE_FETCH_TIMEOUT = "FILE_FETCH_TIMEOUT";
+	const FILE_FETCH_CONNECT_TIMEOUT = "FILE_FETCH_CONNECT_TIMEOUT";
+	const DAEMON_UPDATE_LOGIN_LIMIT = "DAEMON_UPDATE_LOGIN_LIMIT";
+	const DAEMON_FEED_LIMIT = "DAEMON_FEED_LIMIT";
+	const DAEMON_SLEEP_INTERVAL = "DAEMON_SLEEP_INTERVAL";
+	const MAX_CACHE_FILE_SIZE = "MAX_CACHE_FILE_SIZE";
+	const MAX_DOWNLOAD_FILE_SIZE = "MAX_DOWNLOAD_FILE_SIZE";
+	const MAX_FAVICON_FILE_SIZE = "MAX_FAVICON_FILE_SIZE";
+	const CACHE_MAX_DAYS = "CACHE_MAX_DAYS";
+	const MAX_CONDITIONAL_INTERVAL = "MAX_CONDITIONAL_INTERVAL";
+	const DAEMON_UNSUCCESSFUL_DAYS_LIMIT = "DAEMON_UNSUCCESSFUL_DAYS_LIMIT";
+	const LOG_SENT_MAIL = "LOG_SENT_MAIL";
+
+	private const _DEFAULTS = [
+		Config::DB_TYPE => "pgsql",
+		Config::DB_HOST => "db",
+		Config::DB_USER => "",
+		Config::DB_NAME => "",
+		Config::DB_PASS => "",
+		Config::DB_PORT => "5432",
+		Config::MYSQL_CHARSET => "UTF8",
+		Config::SELF_URL_PATH => "",
+		Config::SINGLE_USER_MODE => "",
+		Config::SIMPLE_UPDATE_MODE => "",
+		Config::PHP_EXECUTABLE => "/usr/bin/php",
+		Config::LOCK_DIRECTORY => "lock",
+		Config::CACHE_DIR => "cache",
+		Config::ICONS_DIR => "feed-icons",
+		Config::ICONS_URL => "feed-icons",
+		Config::AUTH_AUTO_CREATE => "true",
+		Config::AUTH_AUTO_LOGIN => "true",
+		Config::FORCE_ARTICLE_PURGE => 0,
+		Config::ENABLE_REGISTRATION => "",
+		Config::SESSION_COOKIE_LIFETIME => 86400,
+		Config::SMTP_FROM_NAME => "Tiny Tiny RSS",
+		Config::SMTP_FROM_ADDRESS => "noreply@localhost",
+		Config::DIGEST_SUBJECT => "[tt-rss] New headlines for last 24 hours",
+		Config::CHECK_FOR_UPDATES => "true",
+		Config::PLUGINS => "auth_internal",
+		Config::LOG_DESTINATION => "sql",
+		Config::LOCAL_OVERRIDE_STYLESHEET => "local-overrides.css",
+		Config::DAEMON_MAX_CHILD_RUNTIME => 1800,
+		Config::DAEMON_MAX_JOBS => 2,
+		Config::FEED_FETCH_TIMEOUT => 45,
+		Config::FEED_FETCH_NO_CACHE_TIMEOUT => 15,
+		Config::FILE_FETCH_TIMEOUT => 45,
+		Config::FILE_FETCH_CONNECT_TIMEOUT => 15,
+		Config::DAEMON_UPDATE_LOGIN_LIMIT => 30,
+		Config::DAEMON_FEED_LIMIT => 500,
+		Config::DAEMON_SLEEP_INTERVAL => 120,
+		Config::MAX_CACHE_FILE_SIZE => 64*1024*1024,
+		Config::MAX_DOWNLOAD_FILE_SIZE => 16*1024*1024,
+		Config::MAX_FAVICON_FILE_SIZE => 1*1024*1024,
+		Config::CACHE_MAX_DAYS => 7,
+		Config::MAX_CONDITIONAL_INTERVAL => 3600*12,
+		Config::DAEMON_UNSUCCESSFUL_DAYS_LIMIT => 30,
+		Config::LOG_SENT_MAIL => "",
+	];
+
+	private static $instance;
+
+	private $params = [];
+
+	public static function get_instance() {
+		if (self::$instance == null)
+			self::$instance = new self();
+
+		return self::$instance;
+	}
+
+	function __construct() {
+		$ref = new ReflectionClass(get_class($this));
+
+		foreach ($ref->getConstants() as $const => $cvalue) {
+			if (strpos($const, "_") !== 0) {
+				$override = getenv($this::_ENVVAR_PREFIX . $const);
+
+				$this->params[$cvalue] = !empty($override) ? $override : $this::_DEFAULTS[$const];
+			}
+		}
+	}
+
+	private function _get(string $param) {
+		return $this->params[$param];
+	}
+
+	private function _add(string $param, string $default) {
+		$override = getenv($this::_ENVVAR_PREFIX . $param);
+
+		$this->params[$param] = !empty($override) ? $override : $default;
+	}
+
+	static function add(string $param, string $default) {
+		$instance = self::get_instance();
+
+		return $instance->_add($param, $default);
+	}
+
+	static function get(string $param) {
+		$instance = self::get_instance();
+
+		return $instance->_get($param);
+	}
+
+}
diff --git a/classes/db.php b/classes/db.php
index 490cecd57..cbfb9e598 100755
--- a/classes/db.php
+++ b/classes/db.php
@@ -17,13 +17,13 @@ class Db
 	// normal usage is Db::pdo()->prepare(...) etc
 	public function pdo_connect() {
 
-		$db_port = defined('DB_PORT') && DB_PORT ? ';port=' . DB_PORT : '';
-		$db_host = defined('DB_HOST') && DB_HOST ? ';host=' . DB_HOST : '';
+		$db_port = Config::get(Config::DB_PORT) ? ';port=' . Config::get(Config::DB_PORT) : '';
+		$db_host = Config::get(Config::DB_HOST) ? ';host=' . Config::get(Config::DB_HOST) : '';
 
 		try {
-			$pdo = new PDO(DB_TYPE . ':dbname=' . DB_NAME . $db_host . $db_port,
-				DB_USER,
-				DB_PASS);
+			$pdo = new PDO(Config::get(Config::DB_TYPE) . ':dbname=' . Config::get(Config::DB_NAME) . $db_host . $db_port,
+				Config::get(Config::DB_USER),
+				Config::get(Config::DB_PASS));
 		} catch (Exception $e) {
 			print "<pre>Exception while creating PDO object:" . $e->getMessage() . "</pre>";
 			exit(101);
@@ -31,18 +31,18 @@ class Db
 
 		$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
 
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 
 			$pdo->query("set client_encoding = 'UTF-8'");
 			$pdo->query("set datestyle = 'ISO, european'");
 			$pdo->query("set TIME ZONE 0");
 			$pdo->query("set cpu_tuple_cost = 0.5");
 
-		} else if (DB_TYPE == "mysql") {
+		} else if (Config::get(Config::DB_TYPE) == "mysql") {
 			$pdo->query("SET time_zone = '+0:0'");
 
-			if (defined('MYSQL_CHARSET') && MYSQL_CHARSET) {
-				$pdo->query("SET NAMES " . MYSQL_CHARSET);
+			if (defined('Config::get(Config::MYSQL_CHARSET)') && Config::get(Config::MYSQL_CHARSET)) {
+				$pdo->query("SET NAMES " . Config::get(Config::MYSQL_CHARSET));
 			}
 		}
 
@@ -68,7 +68,7 @@ class Db
 	}
 
 	public static function sql_random_function() {
-		if (DB_TYPE == "mysql") {
+		if (Config::get(Config::DB_TYPE) == "mysql") {
 			return "RAND()";
 		} else {
 			return "RANDOM()";
diff --git a/classes/digest.php b/classes/digest.php
index e0c23d705..a6a0c47de 100644
--- a/classes/digest.php
+++ b/classes/digest.php
@@ -8,9 +8,9 @@ class Digest
 
 		Debug::log("Sending digests, batch of max $user_limit users, headline limit = $limit");
 
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$interval_qpart = "last_digest_sent < NOW() - INTERVAL '1 days'";
-		} else /* if (DB_TYPE == "mysql") */ {
+		} else /* if (Config::get(Config::DB_TYPE) == "mysql") */ {
 			$interval_qpart = "last_digest_sent < DATE_SUB(NOW(), INTERVAL 1 DAY)";
 		}
 
@@ -48,11 +48,11 @@ class Digest
 
 						$mailer = new Mailer();
 
-						//$rc = $mail->quickMail($line["email"], $line["login"], DIGEST_SUBJECT, $digest, $digest_text);
+						//$rc = $mail->quickMail($line["email"], $line["login"], Config::get(Config::DIGEST_SUBJECT), $digest, $digest_text);
 
 						$rc = $mailer->mail(["to_name" => $line["login"],
 							"to_address" => $line["email"],
-							"subject" => DIGEST_SUBJECT,
+							"subject" => Config::get(Config::DIGEST_SUBJECT),
 							"message" => $digest_text,
 							"message_html" => $digest]);
 
@@ -91,19 +91,19 @@ class Digest
 
 		$tpl->setVariable('CUR_DATE', date('Y/m/d', $local_ts));
 		$tpl->setVariable('CUR_TIME', date('G:i', $local_ts));
-		$tpl->setVariable('TTRSS_HOST', SELF_URL_PATH);
+		$tpl->setVariable('TTRSS_HOST', Config::get(Config::get(Config::SELF_URL_PATH)));
 
 		$tpl_t->setVariable('CUR_DATE', date('Y/m/d', $local_ts));
 		$tpl_t->setVariable('CUR_TIME', date('G:i', $local_ts));
-		$tpl_t->setVariable('TTRSS_HOST', SELF_URL_PATH);
+		$tpl_t->setVariable('TTRSS_HOST', Config::get(Config::get(Config::SELF_URL_PATH)));
 
 		$affected_ids = array();
 
 		$days = (int) $days;
 
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$interval_qpart = "ttrss_entries.date_updated > NOW() - INTERVAL '$days days'";
-		} else /* if (DB_TYPE == "mysql") */ {
+		} else /* if (Config::get(Config::DB_TYPE) == "mysql") */ {
 			$interval_qpart = "ttrss_entries.date_updated > DATE_SUB(NOW(), INTERVAL $days DAY)";
 		}
 
diff --git a/classes/diskcache.php b/classes/diskcache.php
index 94f645f32..9c594acc5 100644
--- a/classes/diskcache.php
+++ b/classes/diskcache.php
@@ -191,7 +191,7 @@ class DiskCache {
 	];
 
 	public function __construct($dir) {
-		$this->dir = CACHE_DIR . "/" . basename(clean($dir));
+		$this->dir = Config::get(Config::CACHE_DIR) . "/" . basename(clean($dir));
 	}
 
 	public function get_dir() {
@@ -339,7 +339,7 @@ class DiskCache {
 	}
 
 	static function expire() {
-		$dirs = array_filter(glob(CACHE_DIR . "/*"), "is_dir");
+		$dirs = array_filter(glob(Config::get(Config::CACHE_DIR) . "/*"), "is_dir");
 
 		foreach ($dirs as $cache_dir) {
 			$num_deleted = 0;
@@ -349,7 +349,7 @@ class DiskCache {
 
 				if ($files) {
 					foreach ($files as $file) {
-						if (time() - filemtime($file) > 86400*CACHE_MAX_DAYS) {
+						if (time() - filemtime($file) > 86400*Config::get(Config::CACHE_MAX_DAYS)) {
 							unlink($file);
 
 							++$num_deleted;
@@ -396,7 +396,7 @@ class DiskCache {
 
 			$tmppluginhost = new PluginHost();
 
-			$tmppluginhost->load(PLUGINS, PluginHost::KIND_SYSTEM);
+			$tmppluginhost->load(Config::get(Config::PLUGINS), PluginHost::KIND_SYSTEM);
 			//$tmppluginhost->load_data();
 
 			if ($tmppluginhost->run_hooks_until(PluginHost::HOOK_SEND_LOCAL_FILE, true, $filename))
diff --git a/classes/feeditem/common.php b/classes/feeditem/common.php
index f387e0779..8f2b9188b 100755
--- a/classes/feeditem/common.php
+++ b/classes/feeditem/common.php
@@ -179,7 +179,7 @@ abstract class FeedItem_Common extends FeedItem {
 
 			$cat = preg_replace('/[,\'\"]/', "", $cat);
 
-			if (DB_TYPE == "mysql") {
+			if (Config::get(Config::DB_TYPE) == "mysql") {
 				$cat = preg_replace('/[\x{10000}-\x{10FFFF}]/u', "\xEF\xBF\xBD", $cat);
 			}
 
diff --git a/classes/feeds.php b/classes/feeds.php
index b59504c03..eaedc1aee 100755
--- a/classes/feeds.php
+++ b/classes/feeds.php
@@ -186,7 +186,7 @@ class Feeds extends Handler_Protected {
 				$id = $line["id"];
 
 				// frontend doesn't expect pdo returning booleans as strings on mysql
-				if (DB_TYPE == "mysql") {
+				if (Config::get(Config::DB_TYPE) == "mysql") {
 					foreach (["unread", "marked", "published"] as $k) {
 						$line[$k] = $line[$k] === "1";
 					}
@@ -576,7 +576,7 @@ class Feeds extends Handler_Protected {
 
 	function search() {
 		print json_encode([
-			"show_language" => DB_TYPE == "pgsql",
+			"show_language" => Config::get(Config::DB_TYPE) == "pgsql",
 			"show_syntax_help" => count(PluginHost::getInstance()->get_hooks(PluginHost::HOOK_SEARCH)) == 0,
 			"all_languages" => Pref_Feeds::get_ts_languages(),
 			"default_language" => get_pref('DEFAULT_SEARCH_LANGUAGE')
@@ -716,21 +716,21 @@ class Feeds extends Handler_Protected {
 
 		switch ($mode) {
 			case "1day":
-				if (DB_TYPE == "pgsql") {
+				if (Config::get(Config::DB_TYPE) == "pgsql") {
 					$date_qpart = "date_entered < NOW() - INTERVAL '1 day' ";
 				} else {
 					$date_qpart = "date_entered < DATE_SUB(NOW(), INTERVAL 1 DAY) ";
 				}
 				break;
 			case "1week":
-				if (DB_TYPE == "pgsql") {
+				if (Config::get(Config::DB_TYPE) == "pgsql") {
 					$date_qpart = "date_entered < NOW() - INTERVAL '1 week' ";
 				} else {
 					$date_qpart = "date_entered < DATE_SUB(NOW(), INTERVAL 1 WEEK) ";
 				}
 				break;
 			case "2week":
-				if (DB_TYPE == "pgsql") {
+				if (Config::get(Config::DB_TYPE) == "pgsql") {
 					$date_qpart = "date_entered < NOW() - INTERVAL '2 week' ";
 				} else {
 					$date_qpart = "date_entered < DATE_SUB(NOW(), INTERVAL 2 WEEK) ";
@@ -807,7 +807,7 @@ class Feeds extends Handler_Protected {
 
 					$intl = (int) get_pref("FRESH_ARTICLE_MAX_AGE");
 
-					if (DB_TYPE == "pgsql") {
+					if (Config::get(Config::DB_TYPE) == "pgsql") {
 						$match_part = "date_entered > NOW() - INTERVAL '$intl hour' ";
 					} else {
 						$match_part = "date_entered > DATE_SUB(NOW(),
@@ -900,7 +900,7 @@ class Feeds extends Handler_Protected {
 
 			$intl = (int) get_pref("FRESH_ARTICLE_MAX_AGE", $owner_uid);
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$match_part .= " AND date_entered > NOW() - INTERVAL '$intl hour' ";
 			} else {
 				$match_part .= " AND date_entered > DATE_SUB(NOW(), INTERVAL $intl HOUR) ";
@@ -1056,11 +1056,11 @@ class Feeds extends Handler_Protected {
 	}
 
 	static function _get_icon_file($feed_id) {
-		return ICONS_DIR . "/$feed_id.ico";
+		return Config::get(Config::ICONS_DIR) . "/$feed_id.ico";
 	}
 
 	static function _has_icon($id) {
-		return is_file(ICONS_DIR . "/$id.ico") && filesize(ICONS_DIR . "/$id.ico") > 0;
+		return is_file(Config::get(Config::ICONS_DIR) . "/$id.ico") && filesize(Config::get(Config::ICONS_DIR) . "/$id.ico") > 0;
 	}
 
 	static function _get_icon($id) {
@@ -1084,7 +1084,7 @@ class Feeds extends Handler_Protected {
 					$icon = self::_get_icon_file($id);
 
                     if ($icon && file_exists($icon)) {
-						return ICONS_URL . "/" . basename($icon) . "?" . filemtime($icon);
+						return Config::get(Config::ICONS_URL) . "/" . basename($icon) . "?" . filemtime($icon);
 					}
 				}
 				break;
@@ -1332,7 +1332,7 @@ class Feeds extends Handler_Protected {
 				list($search_query_part, $search_words) = self::_search_to_sql($search, $search_language, $owner_uid);
 			}
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$test_sth = $pdo->prepare("select $search_query_part
 					FROM ttrss_entries, ttrss_user_entries WHERE id = ref_id limit 1");
 
@@ -1469,7 +1469,7 @@ class Feeds extends Handler_Protected {
 		} else if ($feed == -6) { // recently read
 			$query_strategy_part = "unread = false AND last_read IS NOT NULL";
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$query_strategy_part .= " AND last_read > NOW() - INTERVAL '1 DAY' ";
 			} else {
 				$query_strategy_part .= " AND last_read > DATE_SUB(NOW(), INTERVAL 1 DAY) ";
@@ -1486,7 +1486,7 @@ class Feeds extends Handler_Protected {
 
 			$intl = (int) get_pref("FRESH_ARTICLE_MAX_AGE", $owner_uid);
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$query_strategy_part .= " AND date_entered > NOW() - INTERVAL '$intl hour' ";
 			} else {
 				$query_strategy_part .= " AND date_entered > DATE_SUB(NOW(), INTERVAL $intl HOUR) ";
@@ -1605,7 +1605,7 @@ class Feeds extends Handler_Protected {
 			if ($feed == -3)
 				$first_id_query_strategy_part = "true";
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$sanity_interval_qpart = "date_entered >= NOW() - INTERVAL '1 hour' AND";
 				$yyiw_qpart = "to_char(date_entered, 'IYYY-IW') AS yyiw";
 
@@ -1705,7 +1705,7 @@ class Feeds extends Handler_Protected {
 		} else {
 			// browsing by tag
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$distinct_columns = str_replace("desc", "", strtolower($order_by));
 				$distinct_qpart = "DISTINCT ON (id, $distinct_columns)";
 			} else {
@@ -1948,10 +1948,10 @@ class Feeds extends Handler_Protected {
 		if ($row = $sth->fetch()) {
 			$owner_uid = $row["owner_uid"];
 
-			if (FORCE_ARTICLE_PURGE != 0) {
-				Debug::log("purge_feed: FORCE_ARTICLE_PURGE is set, overriding interval to " . FORCE_ARTICLE_PURGE, Debug::$LOG_VERBOSE);
+			if (Config::get(Config::FORCE_ARTICLE_PURGE) != 0) {
+				Debug::log("purge_feed: FORCE_ARTICLE_PURGE is set, overriding interval to " . Config::get(Config::FORCE_ARTICLE_PURGE), Debug::$LOG_VERBOSE);
 				$purge_unread = true;
-				$purge_interval = FORCE_ARTICLE_PURGE;
+				$purge_interval = Config::get(Config::FORCE_ARTICLE_PURGE);
 			} else {
 				$purge_unread = get_pref("PURGE_UNREAD_ARTICLES", $owner_uid, false);
 			}
@@ -1970,7 +1970,7 @@ class Feeds extends Handler_Protected {
 			else
 				$query_limit = "";
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$sth = $pdo->prepare("DELETE FROM ttrss_user_entries
 					USING ttrss_entries
 					WHERE ttrss_entries.id = ref_id AND
@@ -2153,7 +2153,7 @@ class Feeds extends Handler_Protected {
 						array_push($query_keywords, "(".SUBSTRING_FOR_DATE."(updated,1,LENGTH('$k')) $not = '$k')");
 					} else {
 
-						if (DB_TYPE == "pgsql") {
+						if (Config::get(Config::DB_TYPE) == "pgsql") {
 							$k = mb_strtolower($k);
 							array_push($search_query_leftover, $not ? "!$k" : $k);
 						} else {
@@ -2168,7 +2168,7 @@ class Feeds extends Handler_Protected {
 
 		if (count($search_query_leftover) > 0) {
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 
 				// if there's no joiners consider this a "simple" search and
 				// concatenate everything with &, otherwise don't try to mess with tsquery syntax
diff --git a/classes/handler/public.php b/classes/handler/public.php
index 3910cf7c1..79dff37b5 100755
--- a/classes/handler/public.php
+++ b/classes/handler/public.php
@@ -43,7 +43,7 @@ class Handler_Public extends Handler {
 			$user_plugins = get_pref("_ENABLED_PLUGINS", $owner_uid);
 
 			$tmppluginhost = new PluginHost();
-			$tmppluginhost->load(PLUGINS, PluginHost::KIND_ALL);
+			$tmppluginhost->load(Config::get(Config::PLUGINS), PluginHost::KIND_ALL);
 			$tmppluginhost->load((string)$user_plugins, PluginHost::KIND_USER, $owner_uid);
 			//$tmppluginhost->load_data();
 
@@ -309,7 +309,7 @@ class Handler_Public extends Handler {
 		$format = clean($_REQUEST['format'] ?? "atom");
 		$orig_guid = clean($_REQUEST["orig_guid"] ?? false);
 
-		if (SINGLE_USER_MODE) {
+		if (Config::get(Config::SINGLE_USER_MODE)) {
 			UserHelper::authenticate("admin", null);
 		}
 
@@ -347,7 +347,7 @@ class Handler_Public extends Handler {
 	}
 
 	function login() {
-		if (!SINGLE_USER_MODE) {
+		if (!Config::get(Config::SINGLE_USER_MODE)) {
 
 			$login = clean($_POST["login"]);
 			$password = clean($_POST["password"]);
@@ -355,7 +355,7 @@ class Handler_Public extends Handler {
 			$safe_mode = checkbox_to_sql_bool(clean($_POST["safe_mode"] ?? false));
 
 			if ($remember_me) {
-				@session_set_cookie_params(SESSION_COOKIE_LIFETIME);
+				@session_set_cookie_params(Config::get(Config::SESSION_COOKIE_LIFETIME));
 			} else {
 				@session_set_cookie_params(0);
 			}
@@ -398,7 +398,7 @@ class Handler_Public extends Handler {
 
 			$return = clean($_REQUEST['return']);
 
-			if ($_REQUEST['return'] && mb_strpos($return, SELF_URL_PATH) === 0) {
+			if ($_REQUEST['return'] && mb_strpos($return, Config::get(Config::SELF_URL_PATH)) === 0) {
 				header("Location: " . clean($_REQUEST['return']));
 			} else {
 				header("Location: " . get_self_url_prefix());
@@ -559,7 +559,7 @@ class Handler_Public extends Handler {
 
 						$tpl->setVariable('LOGIN', $login);
 						$tpl->setVariable('RESETPASS_LINK', $resetpass_link);
-						$tpl->setVariable('TTRSS_HOST', SELF_URL_PATH);
+						$tpl->setVariable('TTRSS_HOST', Config::get(Config::SELF_URL_PATH));
 
 						$tpl->addBlock('message');
 
@@ -613,7 +613,7 @@ class Handler_Public extends Handler {
 	function dbupdate() {
 		startup_gettext();
 
-		if (!SINGLE_USER_MODE && $_SESSION["access_level"] < 10) {
+		if (!Config::get(Config::SINGLE_USER_MODE) && $_SESSION["access_level"] < 10) {
 			$_SESSION["login_error_msg"] = __("Your access level is insufficient to run this script.");
 			$this->_render_login_form();
 			exit;
@@ -660,7 +660,7 @@ class Handler_Public extends Handler {
 
 			<?php
 				@$op = clean($_REQUEST["subop"]);
-				$updater = new DbUpdater(Db::pdo(), DB_TYPE, SCHEMA_VERSION);
+				$updater = new DbUpdater(Db::pdo(), Config::get(Config::DB_TYPE), SCHEMA_VERSION);
 
 				if ($op == "performupdate") {
 					if ($updater->is_update_required()) {
@@ -709,7 +709,7 @@ class Handler_Public extends Handler {
 						print "<h2>".T_sprintf("Tiny Tiny RSS database needs update to the latest version (%d to %d).",
 							$updater->get_schema_version(), SCHEMA_VERSION)."</h2>";
 
-						if (DB_TYPE == "mysql") {
+						if (Config::get(Config::DB_TYPE) == "mysql") {
 							print_error("<strong>READ THIS:</strong> Due to MySQL limitations, your database is not completely protected while updating. ".
 								"Errors may put it in an inconsistent state requiring manual rollback. <strong>BACKUP YOUR DATABASE BEFORE CONTINUING.</strong>");
 						} else {
diff --git a/classes/logger.php b/classes/logger.php
index cdc6b240a..6cc33314d 100755
--- a/classes/logger.php
+++ b/classes/logger.php
@@ -42,7 +42,7 @@ class Logger {
 	}
 
 	function __construct() {
-		switch (LOG_DESTINATION) {
+		switch (Config::get(Config::LOG_DESTINATION)) {
 		case "sql":
 			$this->adapter = new Logger_SQL();
 			break;
diff --git a/classes/mailer.php b/classes/mailer.php
index 16be16523..93f778210 100644
--- a/classes/mailer.php
+++ b/classes/mailer.php
@@ -11,15 +11,15 @@ class Mailer {
 		$subject = $params["subject"];
 		$message = $params["message"];
 		$message_html = $params["message_html"];
-		$from_name = $params["from_name"] ? $params["from_name"] : SMTP_FROM_NAME;
-		$from_address = $params["from_address"] ? $params["from_address"] : SMTP_FROM_ADDRESS;
+		$from_name = $params["from_name"] ? $params["from_name"] : Config::get(Config::SMTP_FROM_NAME);
+		$from_address = $params["from_address"] ? $params["from_address"] : Config::get(Config::SMTP_FROM_ADDRESS);
 
 		$additional_headers = $params["headers"] ? $params["headers"] : [];
 
 		$from_combined = $from_name ? "$from_name <$from_address>" : $from_address;
 		$to_combined = $to_name ? "$to_name <$to_address>" : $to_address;
 
-		if (defined('_LOG_SENT_MAIL') && _LOG_SENT_MAIL)
+		if (Config::get(Config::LOG_SENT_MAIL))
 			Logger::get()->log(E_USER_NOTICE, "Sending mail from $from_combined to $to_combined [$subject]: $message");
 
 		// HOOK_SEND_MAIL plugin instructions:
diff --git a/classes/opml.php b/classes/opml.php
index 04d287125..cbc1269e3 100644
--- a/classes/opml.php
+++ b/classes/opml.php
@@ -594,7 +594,7 @@ class OPML extends Handler_Protected {
 		}
 
 		if (is_uploaded_file($_FILES['opml_file']['tmp_name'])) {
-			$tmp_file = (string)tempnam(CACHE_DIR . '/upload', 'opml');
+			$tmp_file = (string)tempnam(Config::get(Config::CACHE_DIR) . '/upload', 'opml');
 
 			$result = move_uploaded_file($_FILES['opml_file']['tmp_name'],
 				$tmp_file);
diff --git a/classes/pref/feeds.php b/classes/pref/feeds.php
index e583a5f51..7c3a40647 100755
--- a/classes/pref/feeds.php
+++ b/classes/pref/feeds.php
@@ -9,7 +9,7 @@ class Pref_Feeds extends Handler_Protected {
 	public static function get_ts_languages() {
 		$rv = [];
 
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$dbh = Db::pdo();
 
 			$res = $dbh->query("SELECT cfgname FROM pg_ts_config");
@@ -441,7 +441,7 @@ class Pref_Feeds extends Handler_Protected {
 		$sth->execute([$feed_id, $_SESSION['uid']]);
 
 		if ($row = $sth->fetch()) {
-			@unlink(ICONS_DIR . "/$feed_id.ico");
+			@unlink(Config::get(Config::ICONS_DIR) . "/$feed_id.ico");
 
 			$sth = $this->pdo->prepare("UPDATE ttrss_feeds SET favicon_avg_color = NULL, favicon_last_checked = '1970-01-01'
 				where id = ?");
@@ -453,7 +453,7 @@ class Pref_Feeds extends Handler_Protected {
 		header("Content-type: text/html");
 
 		if (is_uploaded_file($_FILES['icon_file']['tmp_name'])) {
-			$tmp_file = tempnam(CACHE_DIR . '/upload', 'icon');
+			$tmp_file = tempnam(Config::get(Config::CACHE_DIR) . '/upload', 'icon');
 
 			if (!$tmp_file)
 				return;
@@ -479,7 +479,7 @@ class Pref_Feeds extends Handler_Protected {
 				$sth->execute([$feed_id, $_SESSION['uid']]);
 
 				if ($row = $sth->fetch()) {
-					$new_filename = ICONS_DIR . "/$feed_id.ico";
+					$new_filename = Config::get(Config::ICONS_DIR) . "/$feed_id.ico";
 
 					if (file_exists($new_filename)) unlink($new_filename);
 
@@ -529,7 +529,7 @@ class Pref_Feeds extends Handler_Protected {
 			$local_update_intervals = $update_intervals;
 			$local_update_intervals[0] .= sprintf(" (%s)", $update_intervals[get_pref("DEFAULT_UPDATE_INTERVAL")]);
 
-			if (FORCE_ARTICLE_PURGE == 0) {
+			if (Config::get(Config::FORCE_ARTICLE_PURGE) == 0) {
 				$local_purge_intervals = $purge_intervals;
 				$default_purge_interval = get_pref("PURGE_OLD_DAYS");
 
@@ -539,7 +539,7 @@ class Pref_Feeds extends Handler_Protected {
 				$local_purge_intervals[0] .= " " . sprintf("(%s)", __("Disabled"));
 
 			} else {
-				$purge_interval = FORCE_ARTICLE_PURGE;
+				$purge_interval = Config::get(Config::FORCE_ARTICLE_PURGE);
 				$local_purge_intervals = [ T_nsprintf('%d day', '%d days', $purge_interval, $purge_interval) ];
 			}
 
@@ -550,13 +550,13 @@ class Pref_Feeds extends Handler_Protected {
 					"select" => \Controls\select_feeds_cats("cat_id", $row["cat_id"]),
 				],
 				"plugin_data" => $plugin_data,
-				"force_purge" => (int)FORCE_ARTICLE_PURGE,
+				"force_purge" => (int)Config::get(Config::FORCE_ARTICLE_PURGE),
 				"intervals" => [
 					"update" => $local_update_intervals,
 					"purge" => $local_purge_intervals,
 				],
 				"lang" => [
-					"enabled" => DB_TYPE == "pgsql",
+					"enabled" => Config::get(Config::DB_TYPE) == "pgsql",
 					"default" => get_pref('DEFAULT_SEARCH_LANGUAGE'),
 					"all" => $this::get_ts_languages(),
 					]
@@ -614,7 +614,7 @@ class Pref_Feeds extends Handler_Protected {
 					</fieldset>
 				<?php } ?>
 
-				<?php	if (DB_TYPE == "pgsql") { ?>
+				<?php	if (Config::get(Config::DB_TYPE) == "pgsql") { ?>
 					<fieldset>
 						<label><?= __('Language:') ?></label>
 						<?= \Controls\select_tag("feed_language", "", $this::get_ts_languages(), ["disabled"=> 1]) ?>
@@ -632,7 +632,7 @@ class Pref_Feeds extends Handler_Protected {
 						<?= $this->_batch_toggle_checkbox("update_interval") ?>
 					</fieldset>
 
-					<?php if (FORCE_ARTICLE_PURGE == 0) { ?>
+					<?php if (Config::get(Config::FORCE_ARTICLE_PURGE) == 0) { ?>
 						<fieldset>
 							<label><?= __('Article purging:') ?></label>
 							<?= \Controls\select_hash("purge_interval", "", $local_purge_intervals, ["disabled" => 1]) ?>
@@ -1147,7 +1147,7 @@ class Pref_Feeds extends Handler_Protected {
 
 	function inactiveFeeds() {
 
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$interval_qpart = "NOW() - INTERVAL '3 months'";
 		} else {
 			$interval_qpart = "DATE_SUB(NOW(), INTERVAL 3 MONTH)";
@@ -1228,8 +1228,8 @@ class Pref_Feeds extends Handler_Protected {
 
 			$pdo->commit();
 
-			if (file_exists(ICONS_DIR . "/$id.ico")) {
-				unlink(ICONS_DIR . "/$id.ico");
+			if (file_exists(Config::get(Config::ICONS_DIR) . "/$id.ico")) {
+				unlink(Config::get(Config::ICONS_DIR) . "/$id.ico");
 			}
 
 		} else {
diff --git a/classes/pref/prefs.php b/classes/pref/prefs.php
index adb249dac..1ca5b28be 100644
--- a/classes/pref/prefs.php
+++ b/classes/pref/prefs.php
@@ -236,7 +236,7 @@ class Pref_Prefs extends Handler_Protected {
 
 				$tpl->setVariable('LOGIN', $row["login"]);
 				$tpl->setVariable('NEWMAIL', $email);
-				$tpl->setVariable('TTRSS_HOST', SELF_URL_PATH);
+				$tpl->setVariable('TTRSS_HOST', Config::get(Config::SELF_URL_PATH));
 
 				$tpl->addBlock('message');
 
@@ -625,7 +625,7 @@ class Pref_Prefs extends Handler_Protected {
 					continue;
 				}
 
-				if ($pref_name == "DEFAULT_SEARCH_LANGUAGE" && DB_TYPE != "pgsql") {
+				if ($pref_name == "DEFAULT_SEARCH_LANGUAGE" && Config::get(Config::DB_TYPE) != "pgsql") {
 					continue;
 				}
 
@@ -705,7 +705,7 @@ class Pref_Prefs extends Handler_Protected {
 
 						array_push($listed_boolean_prefs, $pref_name);
 
-						if ($pref_name == "PURGE_UNREAD_ARTICLES" && FORCE_ARTICLE_PURGE != 0) {
+						if ($pref_name == "PURGE_UNREAD_ARTICLES" && Config::get(Config::FORCE_ARTICLE_PURGE) != 0) {
 							$is_disabled = true;
 							$is_checked = true;
 						} else {
@@ -719,9 +719,9 @@ class Pref_Prefs extends Handler_Protected {
 					} else if (in_array($pref_name, ['FRESH_ARTICLE_MAX_AGE',
 							'PURGE_OLD_DAYS', 'LONG_DATE_FORMAT', 'SHORT_DATE_FORMAT'])) {
 
-						if ($pref_name == "PURGE_OLD_DAYS" && FORCE_ARTICLE_PURGE != 0) {
+						if ($pref_name == "PURGE_OLD_DAYS" && Config::get(Config::FORCE_ARTICLE_PURGE) != 0) {
 							$attributes = ["disabled" => true, "required" => true];
-							$value = FORCE_ARTICLE_PURGE;
+							$value = Config::get(Config::FORCE_ARTICLE_PURGE);
 						} else {
 							$attributes = ["required" => true];
 						}
@@ -829,7 +829,7 @@ class Pref_Prefs extends Handler_Protected {
 	private function index_plugins_system() {
 		print_notice("System plugins are enabled in <strong>config.php</strong> for all users.");
 
-		$system_enabled = array_map("trim", explode(",", (string)PLUGINS));
+		$system_enabled = array_map("trim", explode(",", (string)Config::get(Config::PLUGINS)));
 
 		$tmppluginhost = new PluginHost();
 		$tmppluginhost->load_all($tmppluginhost::KIND_ALL, $_SESSION["uid"], true);
@@ -862,7 +862,7 @@ class Pref_Prefs extends Handler_Protected {
 	}
 
 	private function index_plugins_user() {
-		$system_enabled = array_map("trim", explode(",", (string)PLUGINS));
+		$system_enabled = array_map("trim", explode(",", (string)Config::get(Config::PLUGINS)));
 		$user_enabled = array_map("trim", explode(",", get_pref("_ENABLED_PLUGINS")));
 
 		$tmppluginhost = new PluginHost();
@@ -1135,7 +1135,7 @@ class Pref_Prefs extends Handler_Protected {
 				$tpl->readTemplateFromFile("otp_disabled_template.txt");
 
 				$tpl->setVariable('LOGIN', $row["login"]);
-				$tpl->setVariable('TTRSS_HOST', SELF_URL_PATH);
+				$tpl->setVariable('TTRSS_HOST', Config::get(Config::SELF_URL_PATH));
 
 				$tpl->addBlock('message');
 
diff --git a/classes/pref/system.php b/classes/pref/system.php
index bc519a321..35c776463 100644
--- a/classes/pref/system.php
+++ b/classes/pref/system.php
@@ -153,10 +153,10 @@ class Pref_System extends Handler_Administrative {
 		<div dojoType='dijit.layout.AccordionContainer' region='center'>
 			<div dojoType='dijit.layout.AccordionPane' style='padding : 0' title='<i class="material-icons">report</i> <?= __('Event Log') ?>'>
 				<?php
-					if (LOG_DESTINATION == "sql") {
+					if (Config::get(Config::LOG_DESTINATION) == "sql") {
 						$this->_log_viewer($page, $severity);
 					} else {
-						print_notice("Please set LOG_DESTINATION to 'sql' in config.php to enable database logging.");
+						print_notice("Please set Config::get(Config::LOG_DESTINATION) to 'sql' in config.php to enable database logging.");
 					}
 				?>
 			</div>
diff --git a/classes/pref/users.php b/classes/pref/users.php
index 5ac6a7990..f30abe001 100644
--- a/classes/pref/users.php
+++ b/classes/pref/users.php
@@ -86,7 +86,7 @@ class Pref_Users extends Handler_Administrative {
 					<?php while ($row = $sth->fetch()) { ?>
 						<li>
 							<?php
-								$icon_file = ICONS_URL . "/" . $row["id"] . ".ico";
+								$icon_file = Config::get(Config::ICONS_URL) . "/" . $row["id"] . ".ico";
 								$icon = file_exists($icon_file) ? $icon_file : "images/blank_icon.gif";
 							?>
 
diff --git a/classes/rpc.php b/classes/rpc.php
index 95fd0f5ae..4aa3f69d5 100755
--- a/classes/rpc.php
+++ b/classes/rpc.php
@@ -165,8 +165,9 @@ class RPC extends Handler_Protected {
 	function setpanelmode() {
 		$wide = (int) clean($_REQUEST["wide"]);
 
+		// FIXME should this use SESSION_COOKIE_LIFETIME and be renewed periodically?
 		setcookie("ttrss_widescreen", (string)$wide,
-			time() + COOKIE_LIFETIME_LONG);
+			time() + 86400*365);
 
 		print json_encode(array("wide" => $wide));
 	}
@@ -174,7 +175,7 @@ class RPC extends Handler_Protected {
 	static function updaterandomfeed_real() {
 
 		// Test if the feed need a update (update interval exceded).
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$update_limit_qpart = "AND ((
 					ttrss_feeds.update_interval = 0
 					AND ttrss_feeds.last_updated < NOW() - CAST((ttrss_user_prefs.value || ' minutes') AS INTERVAL)
@@ -199,7 +200,7 @@ class RPC extends Handler_Protected {
 		}
 
 		// Test if feed is currently being updated by another process.
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$updstart_thresh_qpart = "AND (ttrss_feeds.last_update_started IS NULL OR ttrss_feeds.last_update_started < NOW() - INTERVAL '5 minutes')";
 		} else {
 			$updstart_thresh_qpart = "AND (ttrss_feeds.last_update_started IS NULL OR ttrss_feeds.last_update_started < DATE_SUB(NOW(), INTERVAL 5 MINUTE))";
@@ -328,7 +329,7 @@ class RPC extends Handler_Protected {
 
 		get_version($git_commit, $git_timestamp);
 
-		if (defined('CHECK_FOR_UPDATES') && CHECK_FOR_UPDATES && $_SESSION["access_level"] >= 10 && $git_timestamp) {
+		if (defined('Config::get(Config::CHECK_FOR_UPDATES)') && Config::get(Config::CHECK_FOR_UPDATES) && $_SESSION["access_level"] >= 10 && $git_timestamp) {
 			$content = @UrlHelper::fetch(["url" => "https://tt-rss.org/version.json"]);
 
 			if ($content) {
@@ -359,9 +360,9 @@ class RPC extends Handler_Protected {
 		}
 
 		$params["safe_mode"] = !empty($_SESSION["safe_mode"]);
-		$params["check_for_updates"] = CHECK_FOR_UPDATES;
-		$params["icons_url"] = ICONS_URL;
-		$params["cookie_lifetime"] = SESSION_COOKIE_LIFETIME;
+		$params["check_for_updates"] = Config::get(Config::CHECK_FOR_UPDATES);
+		$params["icons_url"] = Config::get(Config::ICONS_URL);
+		$params["cookie_lifetime"] = Config::get(Config::SESSION_COOKIE_LIFETIME);
 		$params["default_view_mode"] = get_pref("_DEFAULT_VIEW_MODE");
 		$params["default_view_limit"] = (int) get_pref("_DEFAULT_VIEW_LIMIT");
 		$params["default_view_order_by"] = get_pref("_DEFAULT_VIEW_ORDER_BY");
@@ -390,15 +391,10 @@ class RPC extends Handler_Protected {
 		$params["self_url_prefix"] = get_self_url_prefix();
 		$params["max_feed_id"] = (int) $max_feed_id;
 		$params["num_feeds"] = (int) $num_feeds;
-
 		$params["hotkeys"] = $this->get_hotkeys_map();
-
 		$params["widescreen"] = (int) ($_COOKIE["ttrss_widescreen"] ?? 0);
-
-		$params['simple_update'] = SIMPLE_UPDATE_MODE;
-
+		$params['simple_update'] = Config::get(Config::SIMPLE_UPDATE_MODE);
 		$params["icon_indicator_white"] = $this->image_to_base64("images/indicator_white.gif");
-
 		$params["labels"] = Labels::get_all($_SESSION["uid"]);
 
 		return $params;
@@ -432,8 +428,8 @@ class RPC extends Handler_Protected {
 		$data['cdm_expanded'] = get_pref('CDM_EXPANDED');
 		$data["labels"] = Labels::get_all($_SESSION["uid"]);
 
-		if (LOG_DESTINATION == 'sql' && $_SESSION['access_level'] >= 10) {
-			if (DB_TYPE == 'pgsql') {
+		if (Config::get(Config::LOG_DESTINATION) == 'sql' && $_SESSION['access_level'] >= 10) {
+			if (Config::get(Config::DB_TYPE) == 'pgsql') {
 				$log_interval = "created_at > NOW() - interval '1 hour'";
 			} else {
 				$log_interval = "created_at > DATE_SUB(NOW(), INTERVAL 1 HOUR)";
@@ -452,13 +448,13 @@ class RPC extends Handler_Protected {
 			}
 		}
 
-		if (file_exists(LOCK_DIRECTORY . "/update_daemon.lock")) {
+		if (file_exists(Config::get(Config::LOCK_DIRECTORY) . "/update_daemon.lock")) {
 
 			$data['daemon_is_running'] = (int) file_is_locked("update_daemon.lock");
 
 			if (time() - ($_SESSION["daemon_stamp_check"] ?? 0) > 30) {
 
-				$stamp = (int) @file_get_contents(LOCK_DIRECTORY . "/update_daemon.stamp");
+				$stamp = (int) @file_get_contents(Config::get(Config::LOCK_DIRECTORY) . "/update_daemon.stamp");
 
 				if ($stamp) {
 					$stamp_delta = time() - $stamp;
diff --git a/classes/rssutils.php b/classes/rssutils.php
index 30d08328f..5dcbb48d6 100755
--- a/classes/rssutils.php
+++ b/classes/rssutils.php
@@ -34,9 +34,9 @@ class RSSUtils {
 		$pdo = Db::pdo();
 		$sth = $pdo->prepare("SELECT id FROM ttrss_feeds WHERE id = ?");
 
-		// check icon files once every CACHE_MAX_DAYS days
-		$icon_files = array_filter(glob(ICONS_DIR . "/*.ico"),
-			function($f) { return filemtime($f) < time() - 86400*CACHE_MAX_DAYS; });
+		// check icon files once every Config::get(Config::CACHE_MAX_DAYS) days
+		$icon_files = array_filter(glob(Config::get(Config::ICONS_DIR) . "/*.ico"),
+			function($f) { return filemtime($f) < time() - 86400 * Config::get(Config::CACHE_MAX_DAYS); });
 
 		foreach ($icon_files as $icon) {
 			$feed_id = basename($icon, ".ico");
@@ -52,26 +52,28 @@ class RSSUtils {
 		}
 	}
 
-	static function update_daemon_common($limit = DAEMON_FEED_LIMIT, $options = []) {
+	static function update_daemon_common($limit = null, $options = []) {
 		$schema_version = get_schema_version();
 
+		if (!$limit) $limit = Config::get(Config::DAEMON_FEED_LIMIT);
+
 		if ($schema_version != SCHEMA_VERSION) {
 			die("Schema version is wrong, please upgrade the database.\n");
 		}
 
 		$pdo = Db::pdo();
 
-		if (!SINGLE_USER_MODE && DAEMON_UPDATE_LOGIN_LIMIT > 0) {
-			if (DB_TYPE == "pgsql") {
-				$login_thresh_qpart = "AND ttrss_users.last_login >= NOW() - INTERVAL '".DAEMON_UPDATE_LOGIN_LIMIT." days'";
+		if (!Config::get(Config::SINGLE_USER_MODE) && Config::get(Config::DAEMON_UPDATE_LOGIN_LIMIT) > 0) {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
+				$login_thresh_qpart = "AND ttrss_users.last_login >= NOW() - INTERVAL '".Config::get(Config::DAEMON_UPDATE_LOGIN_LIMIT)." days'";
 			} else {
-				$login_thresh_qpart = "AND ttrss_users.last_login >= DATE_SUB(NOW(), INTERVAL ".DAEMON_UPDATE_LOGIN_LIMIT." DAY)";
+				$login_thresh_qpart = "AND ttrss_users.last_login >= DATE_SUB(NOW(), INTERVAL ".Config::get(Config::DAEMON_UPDATE_LOGIN_LIMIT)." DAY)";
 			}
 		} else {
 			$login_thresh_qpart = "";
 		}
 
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$update_limit_qpart = "AND ((
 					ttrss_feeds.update_interval = 0
 					AND ttrss_user_prefs.value != '-1'
@@ -96,7 +98,7 @@ class RSSUtils {
 		}
 
 		// Test if feed is currently being updated by another process.
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$updstart_thresh_qpart = "AND (last_update_started IS NULL OR last_update_started < NOW() - INTERVAL '10 minutes')";
 		} else {
 			$updstart_thresh_qpart = "AND (last_update_started IS NULL OR last_update_started < DATE_SUB(NOW(), INTERVAL 10 MINUTE))";
@@ -106,7 +108,7 @@ class RSSUtils {
 
 		// Update the least recently updated feeds first
 		$query_order = "ORDER BY last_updated";
-		if (DB_TYPE == "pgsql") $query_order .= " NULLS FIRST";
+		if (Config::get(Config::DB_TYPE) == "pgsql") $query_order .= " NULLS FIRST";
 
 		$query = "SELECT DISTINCT ttrss_feeds.feed_url, ttrss_feeds.last_updated
 			FROM
@@ -182,7 +184,7 @@ class RSSUtils {
 				if (self::function_enabled('passthru')) {
 					$exit_code = 0;
 
-					passthru(PHP_EXECUTABLE . " update.php --update-feed " . $tline["id"] . " --pidlock feed-" . $tline["id"] . " $quiet $log $log_level", $exit_code);
+					passthru(Config::get(Config::PHP_EXECUTABLE) . " update.php --update-feed " . $tline["id"] . " --pidlock feed-" . $tline["id"] . " $quiet $log $log_level", $exit_code);
 
 					Debug::log(sprintf("<= %.4f (sec) exit code: %d", microtime(true) - $fstarted, $exit_code));
 
@@ -275,7 +277,7 @@ class RSSUtils {
 			$pluginhost = new PluginHost();
 			$user_plugins = get_pref("_ENABLED_PLUGINS", $owner_uid);
 
-			$pluginhost->load(PLUGINS, PluginHost::KIND_ALL);
+			$pluginhost->load(Config::get(Config::PLUGINS), PluginHost::KIND_ALL);
 			$pluginhost->load((string)$user_plugins, PluginHost::KIND_USER, $owner_uid);
 			//$pluginhost->load_data();
 
@@ -288,7 +290,7 @@ class RSSUtils {
 			if (!$basic_info) {
 				$feed_data = UrlHelper::fetch($fetch_url, false,
 					$auth_login, $auth_pass, false,
-					FEED_FETCH_TIMEOUT,
+					Config::get(Config::FEED_FETCH_TIMEOUT),
 					0);
 
 				$feed_data = trim($feed_data);
@@ -395,12 +397,12 @@ class RSSUtils {
 
 		$date_feed_processed = date('Y-m-d H:i');
 
-		$cache_filename = CACHE_DIR . "/feeds/" . sha1($fetch_url) . ".xml";
+		$cache_filename = Config::get(Config::CACHE_DIR) . "/feeds/" . sha1($fetch_url) . ".xml";
 
 		$pluginhost = new PluginHost();
 		$user_plugins = get_pref("_ENABLED_PLUGINS", $owner_uid);
 
-		$pluginhost->load(PLUGINS, PluginHost::KIND_ALL);
+		$pluginhost->load(Config::get(Config::PLUGINS), PluginHost::KIND_ALL);
 		$pluginhost->load((string)$user_plugins, PluginHost::KIND_USER, $owner_uid);
 		//$pluginhost->load_data();
 
@@ -455,7 +457,7 @@ class RSSUtils {
 				Debug::log("not using CURL due to open_basedir restrictions", Debug::$LOG_VERBOSE);
 			}
 
-			if (time() - strtotime($last_unconditional) > MAX_CONDITIONAL_INTERVAL) {
+			if (time() - strtotime($last_unconditional) > Config::get(Config::MAX_CONDITIONAL_INTERVAL)) {
 				Debug::log("maximum allowed interval for conditional requests exceeded, forcing refetch", Debug::$LOG_VERBOSE);
 
 				$force_refetch = true;
@@ -469,7 +471,7 @@ class RSSUtils {
 				"url" => $fetch_url,
 				"login" => $auth_login,
 				"pass" => $auth_pass,
-				"timeout" => $no_cache ? FEED_FETCH_NO_CACHE_TIMEOUT : FEED_FETCH_TIMEOUT,
+				"timeout" => $no_cache ? Config::get(Config::FEED_FETCH_NO_CACHE_TIMEOUT) : Config::get(Config::FEED_FETCH_TIMEOUT),
 				"last_modified" => $force_refetch ? "" : $stored_last_modified
 			]);
 
@@ -488,7 +490,7 @@ class RSSUtils {
 			}
 
 			// cache vanilla feed data for re-use
-			if ($feed_data && !$auth_pass && !$auth_login && is_writable(CACHE_DIR . "/feeds")) {
+			if ($feed_data && !$auth_pass && !$auth_login && is_writable(Config::get(Config::CACHE_DIR) . "/feeds")) {
 				$new_rss_hash = sha1($feed_data);
 
 				if ($new_rss_hash != $rss_hash) {
@@ -561,7 +563,7 @@ class RSSUtils {
 			Debug::log("language: $feed_language", Debug::$LOG_VERBOSE);
 			Debug::log("processing feed data...", Debug::$LOG_VERBOSE);
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$favicon_interval_qpart = "favicon_last_checked < NOW() - INTERVAL '12 hour'";
 			} else {
 				$favicon_interval_qpart = "favicon_last_checked < DATE_SUB(NOW(), INTERVAL 12 HOUR)";
@@ -591,7 +593,7 @@ class RSSUtils {
 				/* terrible hack: if we crash on floicon shit here, we won't check
 				 * the icon avgcolor again (unless the icon got updated) */
 
-				$favicon_file = ICONS_DIR . "/$feed.ico";
+				$favicon_file = Config::get(Config::ICONS_DIR) . "/$feed.ico";
 				$favicon_modified = file_exists($favicon_file) ? filemtime($favicon_file) : -1;
 
 				Debug::log("checking favicon for feed $feed...", Debug::$LOG_VERBOSE);
@@ -755,7 +757,7 @@ class RSSUtils {
 							$e->type, $e->length, $e->title, $e->width, $e->height);
 
 						// Yet another episode of "mysql utf8_general_ci is gimped"
-						if (DB_TYPE == "mysql" && MYSQL_CHARSET != "UTF8MB4") {
+						if (Config::get(Config::DB_TYPE) == "mysql" && Config::get(Config::MYSQL_CHARSET) != "UTF8MB4") {
 							for ($i = 0; $i < count($e_item); $i++) {
 								if (is_string($e_item[$i])) {
 									$e_item[$i] = self::strip_utf8mb4($e_item[$i]);
@@ -833,7 +835,7 @@ class RSSUtils {
 				Debug::log("plugin data: $entry_plugin_data", Debug::$LOG_VERBOSE);
 
 				// Workaround: 4-byte unicode requires utf8mb4 in MySQL. See https://tt-rss.org/forum/viewtopic.php?f=1&t=3377&p=20077#p20077
-				if (DB_TYPE == "mysql" && MYSQL_CHARSET != "UTF8MB4") {
+				if (Config::get(Config::DB_TYPE) == "mysql" && Config::get(Config::MYSQL_CHARSET) != "UTF8MB4") {
 					foreach ($article as $k => $v) {
 						// i guess we'll have to take the risk of 4byte unicode labels & tags here
 						if (is_string($article[$k])) {
@@ -1079,7 +1081,7 @@ class RSSUtils {
 
 					Debug::log("resulting RID: $entry_ref_id, IID: $entry_int_id", Debug::$LOG_VERBOSE);
 
-					if (DB_TYPE == "pgsql")
+					if (Config::get(Config::DB_TYPE) == "pgsql")
 						$tsvector_qpart = "tsvector_combined = to_tsvector(:ts_lang, :ts_content),";
 					else
 						$tsvector_qpart = "";
@@ -1107,7 +1109,7 @@ class RSSUtils {
 						":lang" => $entry_language,
 						":id" => $ref_id];
 
-					if (DB_TYPE == "pgsql") {
+					if (Config::get(Config::DB_TYPE) == "pgsql") {
 						$params[":ts_lang"] = $feed_language;
 						$params[":ts_content"] = mb_substr(strip_tags($entry_title . " " . $entry_content), 0, 900000);
 					}
@@ -1298,7 +1300,7 @@ class RSSUtils {
 
 						$file_content = UrlHelper::fetch(array("url" => $src,
 							"http_referrer" => $src,
-							"max_size" => MAX_CACHE_FILE_SIZE));
+							"max_size" => Config::get(Config::MAX_CACHE_FILE_SIZE)));
 
 						if ($file_content) {
 							$cache->put($local_filename, $file_content);
@@ -1328,7 +1330,7 @@ class RSSUtils {
 
 			$file_content = UrlHelper::fetch(array("url" => $url,
 				"http_referrer" => $url,
-				"max_size" => MAX_CACHE_FILE_SIZE));
+				"max_size" => Config::get(Config::MAX_CACHE_FILE_SIZE)));
 
 			if ($file_content) {
 				$cache->put($local_filename, $file_content);
@@ -1375,7 +1377,7 @@ class RSSUtils {
 
 		$pdo = Db::pdo();
 
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$pdo->query("DELETE FROM ttrss_error_log
 				WHERE created_at < NOW() - INTERVAL '7 days'");
 		} else {
@@ -1396,8 +1398,8 @@ class RSSUtils {
 
 		$num_deleted = 0;
 
-		if (is_writable(LOCK_DIRECTORY)) {
-			$files = glob(LOCK_DIRECTORY . "/*.lock");
+		if (is_writable(Config::get(Config::LOCK_DIRECTORY))) {
+			$files = glob(Config::get(Config::LOCK_DIRECTORY) . "/*.lock");
 
 			if ($files) {
 				foreach ($files as $file) {
@@ -1589,9 +1591,9 @@ class RSSUtils {
 
 			$days = DAEMON_UNSUCCESSFUL_DAYS_LIMIT;
 
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$interval_query = "last_successful_update < NOW() - INTERVAL '$days days' AND last_updated > NOW() - INTERVAL '1 days'";
-			} else /* if (DB_TYPE == "mysql") */ {
+			} else /* if (Config::get(Config::DB_TYPE) == "mysql") */ {
 				$interval_query = "last_successful_update < DATE_SUB(NOW(), INTERVAL $days DAY) AND last_updated > DATE_SUB(NOW(), INTERVAL 1 DAY)";
 			}
 
@@ -1643,7 +1645,7 @@ class RSSUtils {
 	}
 
 	static function check_feed_favicon($site_url, $feed) {
-		$icon_file = ICONS_DIR . "/$feed.ico";
+		$icon_file = Config::get(Config::ICONS_DIR) . "/$feed.ico";
 
 		$favicon_url = self::get_favicon_url($site_url);
 		if (!$favicon_url) {
@@ -1654,7 +1656,7 @@ class RSSUtils {
 		// Limiting to "image" type misses those served with text/plain
 		$contents = UrlHelper::fetch([
 			'url' => $favicon_url,
-			'max_size' => MAX_FAVICON_FILE_SIZE,
+			'max_size' => Config::get(Config::MAX_FAVICON_FILE_SIZE),
 			//'type' => 'image',
 		]);
 		if (!$contents) {
diff --git a/classes/urlhelper.php b/classes/urlhelper.php
index 8717d02c3..42aa069e6 100644
--- a/classes/urlhelper.php
+++ b/classes/urlhelper.php
@@ -209,7 +209,7 @@ class UrlHelper {
 		$last_modified = isset($options["last_modified"]) ? $options["last_modified"] : "";
 		$useragent = isset($options["useragent"]) ? $options["useragent"] : false;
 		$followlocation = isset($options["followlocation"]) ? $options["followlocation"] : true;
-		$max_size = isset($options["max_size"]) ? $options["max_size"] : MAX_DOWNLOAD_FILE_SIZE; // in bytes
+		$max_size = isset($options["max_size"]) ? $options["max_size"] : Config::get(Config::MAX_DOWNLOAD_FILE_SIZE); // in bytes
 		$http_accept = isset($options["http_accept"]) ? $options["http_accept"] : false;
 		$http_referrer = isset($options["http_referrer"]) ? $options["http_referrer"] : false;
 
@@ -250,8 +250,8 @@ class UrlHelper {
 			if (count($curl_http_headers) > 0)
 				curl_setopt($ch, CURLOPT_HTTPHEADER, $curl_http_headers);
 
-			curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout ? $timeout : FILE_FETCH_CONNECT_TIMEOUT);
-			curl_setopt($ch, CURLOPT_TIMEOUT, $timeout ? $timeout : FILE_FETCH_TIMEOUT);
+			curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout ? $timeout : Config::get(Config::FILE_FETCH_CONNECT_TIMEOUT));
+			curl_setopt($ch, CURLOPT_TIMEOUT, $timeout ? $timeout : Config::get(Config::FILE_FETCH_TIMEOUT));
 			curl_setopt($ch, CURLOPT_FOLLOWLOCATION, !ini_get("open_basedir") && $followlocation);
 			curl_setopt($ch, CURLOPT_MAXREDIRS, 20);
 			curl_setopt($ch, CURLOPT_BINARYTRANSFER, true);
@@ -395,7 +395,7 @@ class UrlHelper {
 						),
 						'method' => 'GET',
 						'ignore_errors' => true,
-						'timeout' => $timeout ? $timeout : FILE_FETCH_TIMEOUT,
+						'timeout' => $timeout ? $timeout : Config::get(Config::FILE_FETCH_TIMEOUT),
 						'protocol_version'=> 1.1)
 				  );
 
@@ -417,7 +417,7 @@ class UrlHelper {
 
 			$old_error = error_get_last();
 
-			$fetch_effective_url = self::resolve_redirects($url, $timeout ? $timeout : FILE_FETCH_CONNECT_TIMEOUT);
+			$fetch_effective_url = self::resolve_redirects($url, $timeout ? $timeout : Config::get(Config::FILE_FETCH_CONNECT_TIMEOUT));
 
 			if (!self::validate($fetch_effective_url, true)) {
 				$fetch_last_error = "URL received after redirection failed extended validation.";
diff --git a/classes/userhelper.php b/classes/userhelper.php
index 7fe1e5557..82a2fe05f 100644
--- a/classes/userhelper.php
+++ b/classes/userhelper.php
@@ -2,7 +2,7 @@
 class UserHelper {
 
 	static function authenticate(string $login = null, string $password = null, bool $check_only = false, string $service = null) {
-		if (!SINGLE_USER_MODE) {
+		if (!Config::get(Config::SINGLE_USER_MODE)) {
 			$user_id = false;
 			$auth_module = false;
 
@@ -88,7 +88,7 @@ class UserHelper {
 	static function login_sequence() {
 		$pdo = Db::pdo();
 
-		if (SINGLE_USER_MODE) {
+		if (Config::get(Config::SINGLE_USER_MODE)) {
 			@session_start();
 			self::authenticate("admin", null);
 			startup_gettext();
@@ -98,7 +98,7 @@ class UserHelper {
 
 			if (empty($_SESSION["uid"])) {
 
-				if (AUTH_AUTO_LOGIN && self::authenticate(null, null)) {
+				if (Config::get(Config::AUTH_AUTO_LOGIN) && self::authenticate(null, null)) {
 					$_SESSION["ref_schema_version"] = get_schema_version(true);
 				} else {
 					 self::authenticate(null, null, true);
diff --git a/config.php-dist b/config.php-dist
index 2ee1c719d..b633a7b6b 100644
--- a/config.php-dist
+++ b/config.php-dist
@@ -1,146 +1,18 @@
 <?php
-	// *******************************************
-	// *** Database configuration (important!) ***
-	// *******************************************
+	/*
+		This file can be used to customize global defaults if environment method is not available (i.e. no Docker).
 
-	define('DB_TYPE', '%DB_TYPE'); // pgsql or mysql
-	define('DB_HOST', '%DB_HOST');
-	define('DB_USER', '%DB_USER');
-	define('DB_NAME', '%DB_NAME');
-	define('DB_PASS', '%DB_PASS');
-	define('DB_PORT', '%DB_PORT'); // usually 5432 for PostgreSQL, 3306 for MySQL
+		Use the following syntax to override defaults (options are declared in classes/config.php, prefixed by TTRSS_):
 
-	define('MYSQL_CHARSET', 'UTF8');
-	// Connection charset for MySQL. If you have a legacy database and/or experience
-	// garbage unicode characters with this option, try setting it to a blank string.
+		putenv('TTRSS_DB_HOST=myserver')
+		putenv('TTRSS_SELF_URL_PATH=http://example.com/tt-rss')
 
-	// ***********************************
-	// *** Basic settings (important!) ***
-	// ***********************************
+		Plugin-required constants also go here, using define():
 
-	define('SELF_URL_PATH', '%SELF_URL_PATH');
-	// This should be set to a fully qualified URL used to access
-	// your tt-rss instance over the net, such as: https://example.org/tt-rss/
-	// The value should be a constant string literal. Please don't use
-	// PHP server variables here - you might introduce security
-	// issues on your install and cause hard to debug problems.
-	// If your tt-rss instance is behind a reverse proxy, use the external URL.
+		define('LEGACY_CONSTANT', 'value');
 
-	define('SINGLE_USER_MODE', false);
-	// Operate in single user mode, disables all functionality related to
-	// multiple users and authentication. Enabling this assumes you have
-	// your tt-rss directory protected by other means (e.g. http auth).
+		etc.
 
-	define('SIMPLE_UPDATE_MODE', false);
-	// Enables fallback update mode where tt-rss tries to update feeds in
-	// background while tt-rss is open in your browser.
-	// If you don't have a lot of feeds and don't want to or can't run
-	// background processes while not running tt-rss, this method is generally
-	// viable to keep your feeds up to date.
-	// Still, there are more robust (and recommended) updating methods
-	// available, you can read about them here: https://tt-rss.org/wiki/UpdatingFeeds
+		See this page for more information: https://tt-rss.org/wiki/GlobalConfig
+	*/
 
-	// *****************************
-	// *** Files and directories ***
-	// *****************************
-
-	define('PHP_EXECUTABLE', '/usr/bin/php');
-	// Path to PHP *COMMAND LINE* executable, used for various command-line tt-rss
-	// programs and update daemon. Do not try to use CGI binary here, it won't work.
-	// If you see HTTP headers being displayed while running tt-rss scripts,
-	// then most probably you are using the CGI binary. If you are unsure what to
-	// put in here, ask your hosting provider.
-
-	define('LOCK_DIRECTORY', 'lock');
-	// Directory for lockfiles, must be writable to the user you run
-	// daemon process or cronjobs under.
-
-	define('CACHE_DIR', 'cache');
-	// Local cache directory for RSS feed content.
-
-	define('ICONS_DIR', "feed-icons");
-	define('ICONS_URL', "feed-icons");
-	// Local and URL path to the directory, where feed favicons are stored.
-	// Unless you really know what you're doing, please keep those relative
-	// to tt-rss main directory.
-
-	// **********************
-	// *** Authentication ***
-	// **********************
-
-	// Please see PLUGINS below to configure various authentication modules.
-
-	define('AUTH_AUTO_CREATE', true);
-	// Allow authentication modules to auto-create users in tt-rss internal
-	// database when authenticated successfully.
-
-	define('AUTH_AUTO_LOGIN', true);
-	// Automatically login user on remote or other kind of externally supplied
-	// authentication, otherwise redirect to login form as normal.
-	// If set to true, users won't be able to set application language
-	// and settings profile.
-
-	// *********************
-	// *** Feed settings ***
-	// *********************
-
-	define('FORCE_ARTICLE_PURGE', 0);
-	// When this option is not 0, users ability to control feed purging
-	// intervals is disabled and all articles (which are not starred)
-	// older than this amount of days are purged.
-
-	// **********************************
-	// *** Cookies and login sessions ***
-	// **********************************
-
-	define('SESSION_COOKIE_LIFETIME', 86400);
-	// Default lifetime of a session (e.g. login) cookie. In seconds,
-	// 0 means cookie will be deleted when browser closes.
-
-	// *********************************
-	// *** Email and digest settings ***
-	// *********************************
-
-	// Tiny Tiny RSS sends mail via PHP mail() function, unless handled
-	// by a plugin.
-
-	// If you need SMTP support, take a look here:
-	// https://git.tt-rss.org/fox/ttrss-mailer-smtp
-
-	define('SMTP_FROM_NAME', 'Tiny Tiny RSS');
-	define('SMTP_FROM_ADDRESS', 'noreply@your.domain.dom');
-	// Name, address and subject for sending outgoing mail. This applies
-	// to password reset notifications, digest emails and any other mail.
-
-	define('DIGEST_SUBJECT', '[tt-rss] New headlines for last 24 hours');
-	// Subject line for email digests
-
-	// ***************************************
-	// *** Other settings (less important) ***
-	// ***************************************
-
-	define('CHECK_FOR_UPDATES', true);
-	// Check for updates automatically if running Git version
-
-	define('PLUGINS', 'auth_internal, note');
-	// Comma-separated list of plugins to load automatically for all users.
-	// System plugins have to be specified here. Please enable at least one
-	// authentication plugin here (auth_*).
-	// Users may enable other user plugins from Preferences/Plugins but may not
-	// disable plugins specified in this list.
-	// Disabling auth_internal in this list would automatically disable
-	// reset password link on the login form.
-
-	define('LOG_DESTINATION', 'sql');
-	// Error log destination to use. Possible values: sql (uses internal logging
-	// you can read in Preferences -> System), syslog - logs to system log.
-	// Setting this to blank uses PHP logging (usually to http server
-	// error.log).
-	// Note that feed updating daemons don't use this logging facility
-	// for normal output.
-
-	define('CONFIG_VERSION', 26);
-	// Expected config version. Please update this option in config.php
-	// if necessary (after migrating all new options from this file).
-
-	// vim:ft=php
diff --git a/include/autoload.php b/include/autoload.php
index c02923dba..19e00b9ea 100644
--- a/include/autoload.php
+++ b/include/autoload.php
@@ -1,6 +1,4 @@
 <?php
-	require_once "functions.php";
-
 	spl_autoload_register(function($class) {
 		$namespace = '';
 		$class_name = $class;
diff --git a/include/db-prefs.php b/include/db-prefs.php
deleted file mode 100644
index ce5753638..000000000
--- a/include/db-prefs.php
+++ /dev/null
@@ -1,8 +0,0 @@
-<?php
-	function get_pref($pref_name, $user_id = false, $die_on_error = false) {
-		return Db_Prefs::get()->read($pref_name, $user_id, $die_on_error);
-	}
-
-	function set_pref($pref_name, $value, $user_id = false, $strip_tags = true) {
-		return Db_Prefs::get()->write($pref_name, $value, $user_id, $strip_tags);
-	}
\ No newline at end of file
diff --git a/include/functions.php b/include/functions.php
index 7c4e32963..a698fa79d 100644
--- a/include/functions.php
+++ b/include/functions.php
@@ -1,16 +1,9 @@
 <?php
-	define('EXPECTED_CONFIG_VERSION', 26);
 	define('SCHEMA_VERSION', 140);
 
 	define('LABEL_BASE_INDEX', -1024);
 	define('PLUGIN_FEED_BASE_INDEX', -128);
 
-	define('COOKIE_LIFETIME_LONG', 86400*365);
-
-	// this CSS file is included for everyone (if it exists in themes.local)
-	// on login, registration, and main (index and prefs) pages
-	define('LOCAL_OVERRIDE_STYLESHEET', '.local-overrides.css');
-
 	$fetch_last_error = false;
 	$fetch_last_error_code = false;
 	$fetch_last_content_type = false;
@@ -37,55 +30,26 @@
 	ini_set('display_errors', "false");
 	ini_set('display_startup_errors', "false");
 
-	require_once 'config.php';
+	// config.php is optional
+	if (stream_resolve_include_path("config.php"))
+		require_once "config.php";
 
-	/* Some tunables you can override in config.php using define():	*/
+	require_once "autoload.php";
 
-	if (!defined('FEED_FETCH_TIMEOUT')) 					define('FEED_FETCH_TIMEOUT', 45);
-	// How may seconds to wait for response when requesting feed from a site
-	if (!defined('FEED_FETCH_NO_CACHE_TIMEOUT')) 		define('FEED_FETCH_NO_CACHE_TIMEOUT', 15);
-	// How may seconds to wait for response when requesting feed from a
-	// site when that feed wasn't cached before
-	if (!defined('FILE_FETCH_TIMEOUT')) 					define('FILE_FETCH_TIMEOUT', 45);
-	// Default timeout when fetching files from remote sites
-	if (!defined('FILE_FETCH_CONNECT_TIMEOUT')) 			define('FILE_FETCH_CONNECT_TIMEOUT', 15);
-	// How many seconds to wait for initial response from website when
-	// fetching files from remote sites
-	if (!defined('DAEMON_UPDATE_LOGIN_LIMIT'))			define('DAEMON_UPDATE_LOGIN_LIMIT', 30);
-	// stop updating feeds if users haven't logged in for X days
-	if (!defined('DAEMON_FEED_LIMIT'))						define('DAEMON_FEED_LIMIT', 500);
-	// feed limit for one update batch
-	if (!defined('DAEMON_SLEEP_INTERVAL'))					define('DAEMON_SLEEP_INTERVAL', 120);
-	// default sleep interval between feed updates (sec)
-	if (!defined('MAX_CACHE_FILE_SIZE'))					define('MAX_CACHE_FILE_SIZE', 64*1024*1024);
-	// do not cache files larger than that (bytes)
-	if (!defined('MAX_DOWNLOAD_FILE_SIZE'))				define('MAX_DOWNLOAD_FILE_SIZE', 16*1024*1024);
-	// do not download general files larger than that (bytes)
-	if (!defined('MAX_FAVICON_FILE_SIZE'))					define('MAX_FAVICON_FILE_SIZE', 1*1024*1024);
-	// do not download favicon files larger than that (bytes)
-	if (!defined('CACHE_MAX_DAYS'))							define('CACHE_MAX_DAYS', 7);
-	// max age in days for various automatically cached (temporary) files
-	if (!defined('MAX_CONDITIONAL_INTERVAL'))				define('MAX_CONDITIONAL_INTERVAL', 3600*12);
-	// max interval between forced unconditional updates for servers
-	// not complying with http if-modified-since (seconds)
-	// if (!defined('MAX_FETCH_REQUESTS_PER_HOST')) define('MAX_FETCH_REQUESTS_PER_HOST', 25);
-	// a maximum amount of allowed HTTP requests per destination host
-	// during a single update (i.e. within PHP process lifetime)
-	// this is used to not cause excessive load on the origin server on
-	// e.g. feed subscription when all articles are being processes
-	// (not implemented)
-	if (!defined('DAEMON_UNSUCCESSFUL_DAYS_LIMIT'))		define('DAEMON_UNSUCCESSFUL_DAYS_LIMIT', 30);
-	// automatically disable updates for feeds which failed to
-	// update for this amount of days; 0 disables
-
-	/* tunables end here */
-
-	if (DB_TYPE == "pgsql") {
+	if (Config::get(Config::DB_TYPE) == "pgsql") {
 		define('SUBSTRING_FOR_DATE', 'SUBSTRING_FOR_DATE');
 	} else {
 		define('SUBSTRING_FOR_DATE', 'SUBSTRING');
 	}
 
+	function get_pref($pref_name, $user_id = false, $die_on_error = false) {
+		return Db_Prefs::get()->read($pref_name, $user_id, $die_on_error);
+	}
+
+	function set_pref($pref_name, $value, $user_id = false, $strip_tags = true) {
+		return Db_Prefs::get()->write($pref_name, $value, $user_id, $strip_tags);
+	}
+
 	function get_translations() {
 		$t = array(
 					"auto"  => __("Detect automatically"),
@@ -196,7 +160,6 @@
 		}
 	}
 
-	require_once 'db-prefs.php';
 	require_once 'controls.php';
 	require_once 'controls_compat.php';
 
@@ -375,9 +338,9 @@
 	}
 
 	function file_is_locked($filename) {
-		if (file_exists(LOCK_DIRECTORY . "/$filename")) {
+		if (file_exists(Config::get(Config::LOCK_DIRECTORY) . "/$filename")) {
 			if (function_exists('flock')) {
-				$fp = @fopen(LOCK_DIRECTORY . "/$filename", "r");
+				$fp = @fopen(Config::get(Config::LOCK_DIRECTORY) . "/$filename", "r");
 				if ($fp) {
 					if (flock($fp, LOCK_EX | LOCK_NB)) {
 						flock($fp, LOCK_UN);
@@ -397,11 +360,11 @@
 	}
 
 	function make_lockfile($filename) {
-		$fp = fopen(LOCK_DIRECTORY . "/$filename", "w");
+		$fp = fopen(Config::get(Config::LOCK_DIRECTORY) . "/$filename", "w");
 
 		if ($fp && flock($fp, LOCK_EX | LOCK_NB)) {
 			$stat_h = fstat($fp);
-			$stat_f = stat(LOCK_DIRECTORY . "/$filename");
+			$stat_f = stat(Config::get(Config::LOCK_DIRECTORY) . "/$filename");
 
 			if (strtoupper(substr(PHP_OS, 0, 3)) !== 'WIN') {
 				if ($stat_h["ino"] != $stat_f["ino"] ||
@@ -444,15 +407,15 @@
 	}
 
 	function is_prefix_https() {
-		return parse_url(SELF_URL_PATH, PHP_URL_SCHEME) == 'https';
+		return parse_url(Config::get(Config::SELF_URL_PATH), PHP_URL_SCHEME) == 'https';
 	}
 
-	// this returns SELF_URL_PATH sans ending slash
+	// this returns Config::get(Config::SELF_URL_PATH) sans ending slash
 	function get_self_url_prefix() {
-		if (strrpos(SELF_URL_PATH, "/") === strlen(SELF_URL_PATH)-1) {
-			return substr(SELF_URL_PATH, 0, strlen(SELF_URL_PATH)-1);
+		if (strrpos(Config::get(Config::SELF_URL_PATH), "/") === strlen(Config::get(Config::SELF_URL_PATH))-1) {
+			return substr(Config::get(Config::SELF_URL_PATH), 0, strlen(Config::get(Config::SELF_URL_PATH))-1);
 		} else {
-			return SELF_URL_PATH;
+			return Config::get(Config::SELF_URL_PATH);
 		}
 	}
 
@@ -467,7 +430,7 @@
 	} // function encrypt_password
 
 	function init_plugins() {
-		PluginHost::getInstance()->load(PLUGINS, PluginHost::KIND_ALL);
+		PluginHost::getInstance()->load(Config::get(Config::PLUGINS), PluginHost::KIND_ALL);
 
 		return true;
 	}
diff --git a/include/login_form.php b/include/login_form.php
index 211302a87..168fe50aa 100755
--- a/include/login_form.php
+++ b/include/login_form.php
@@ -16,8 +16,8 @@
 
 	} ?>
 
-	<?php if (theme_exists(LOCAL_OVERRIDE_STYLESHEET)) {
-		echo stylesheet_tag(get_theme_path(LOCAL_OVERRIDE_STYLESHEET));
+	<?php if (theme_exists(Config::get(Config::LOCAL_OVERRIDE_STYLESHEET))) {
+		echo stylesheet_tag(get_theme_path(Config::get(Config::LOCAL_OVERRIDE_STYLESHEET)));
 	} ?>
 
 	<style type="text/css">
@@ -79,7 +79,7 @@
     	},
         bwLimitChange: function(elem) {
         	Cookie.set("ttrss_bwlimit", elem.checked,
-				<?php print SESSION_COOKIE_LIFETIME ?>);
+				<?php print Config::get(Config::SESSION_COOKIE_LIFETIME) ?>);
 	    }
     };
 
@@ -122,7 +122,7 @@
 					   onblur="UtilityApp.fetchProfiles()"
 					   value="<?= $_SESSION["fake_password"] ?? "" ?>"/>
 			</fieldset>
-			<?php if (strpos(PLUGINS, "auth_internal") !== false) { ?>
+			<?php if (strpos(Config::get(Config::PLUGINS), "auth_internal") !== false) { ?>
 				<fieldset class="align-right">
 					<a href="public.php?op=forgotpass"><?= __("I forgot my password") ?></a>
 				</fieldset>
@@ -161,7 +161,7 @@
 			<div dojoType="dijit.Tooltip" connectId="safe_mode_label" position="below" style="display:none">
 				<?= __("Uses default theme and prevents all plugins from loading."); ?>
 			</div>
-			<?php if (SESSION_COOKIE_LIFETIME > 0) { ?>
+			<?php if (Config::get(Config::SESSION_COOKIE_LIFETIME) > 0) { ?>
 
 				<fieldset class="narrow">
 					<label> </label>
diff --git a/include/sanity_check.php b/include/sanity_check.php
index 2786f012f..4831209ba 100755
--- a/include/sanity_check.php
+++ b/include/sanity_check.php
@@ -21,7 +21,7 @@
 
 		$sth = $pdo->prepare("SELECT engine, table_name FROM information_schema.tables WHERE
 				table_schema = ? AND table_name LIKE 'ttrss_%' AND engine != 'InnoDB'");
-		$sth->execute([DB_NAME]);
+		$sth->execute([Config::get(Config::DB_NAME)]);
 
 		$bad_tables = [];
 
@@ -44,8 +44,8 @@
 				array_push($errors, "Please copy config.php-dist to config.php");
 			}
 
-			if (strpos(PLUGINS, "auth_") === false) {
-				array_push($errors, "Please enable at least one authentication module via PLUGINS constant in config.php");
+			if (strpos(Config::get(Config::PLUGINS), "auth_") === false) {
+				array_push($errors, "Please enable at least one authentication module via Config::get(Config::PLUGINS) constant in config.php");
 			}
 
 			if (function_exists('posix_getuid') && posix_getuid() == 0) {
@@ -60,43 +60,25 @@
 				array_push($errors, "PHP UConverter class is missing, it's provided by the Internationalization (intl) module.");
 			}
 
-			if (CONFIG_VERSION != EXPECTED_CONFIG_VERSION) {
-				array_push($errors, "Configuration file (config.php) has incorrect version. Update it with new options from config.php-dist and set CONFIG_VERSION to the correct value.");
+			if (!is_writable(Config::get(Config::CACHE_DIR) . "/images")) {
+				array_push($errors, "Image cache is not writable (chmod -R 777 ".Config::get(Config::CACHE_DIR)."/images)");
 			}
 
-			if (!is_writable(CACHE_DIR . "/images")) {
-				array_push($errors, "Image cache is not writable (chmod -R 777 ".CACHE_DIR."/images)");
+			if (!is_writable(Config::get(Config::CACHE_DIR) . "/upload")) {
+				array_push($errors, "Upload cache is not writable (chmod -R 777 ".Config::get(Config::CACHE_DIR)."/upload)");
 			}
 
-			if (!is_writable(CACHE_DIR . "/upload")) {
-				array_push($errors, "Upload cache is not writable (chmod -R 777 ".CACHE_DIR."/upload)");
+			if (!is_writable(Config::get(Config::CACHE_DIR) . "/export")) {
+				array_push($errors, "Data export cache is not writable (chmod -R 777 ".Config::get(Config::CACHE_DIR)."/export)");
 			}
 
-			if (!is_writable(CACHE_DIR . "/export")) {
-				array_push($errors, "Data export cache is not writable (chmod -R 777 ".CACHE_DIR."/export)");
-			}
-
-			require_once "sanity_config.php";
-
-			if (GENERATED_CONFIG_CHECK != EXPECTED_CONFIG_VERSION) {
-				array_push($errors,
-					"Configuration option checker sanity_config.php is outdated, please recreate it using ./utils/regen_config_checks.sh");
-			}
-
-			foreach (get_required_defines() as $d) {
-				if (!defined($d)) {
-					array_push($errors,
-						"Required configuration file parameter $d is not defined in config.php. You might need to copy it from config.php-dist.");
-				}
-			}
-
-			if (SINGLE_USER_MODE && class_exists("PDO")) {
+			if (Config::get(Config::SINGLE_USER_MODE) && class_exists("PDO")) {
 			    $pdo = Db::pdo();
 
 				$res = $pdo->query("SELECT id FROM ttrss_users WHERE id = 1");
 
 				if (!$res->fetch()) {
-					array_push($errors, "SINGLE_USER_MODE is enabled in config.php but default admin account is not found.");
+					array_push($errors, "Config::get(Config::SINGLE_USER_MODE) is enabled in config.php but default admin account is not found.");
 				}
 			}
 
@@ -107,26 +89,26 @@
 					$ref_self_url_path = preg_replace("/\w+\.php$/", "", $ref_self_url_path);
 				}
 
-				if (SELF_URL_PATH == "http://example.org/tt-rss/") {
+				if (Config::get(Config::SELF_URL_PATH) == "http://example.org/tt-rss/") {
 					$hint = $ref_self_url_path ? "(possible value: <b>$ref_self_url_path</b>)" : "";
 					array_push($errors,
-							"Please set SELF_URL_PATH to the correct value for your server: $hint");
+							"Please set Config::get(Config::SELF_URL_PATH) to the correct value for your server: $hint");
 				}
 
 				if ($ref_self_url_path &&
 					(!defined('_SKIP_SELF_URL_PATH_CHECKS') || !_SKIP_SELF_URL_PATH_CHECKS) &&
-					SELF_URL_PATH != $ref_self_url_path && SELF_URL_PATH != mb_substr($ref_self_url_path, 0, mb_strlen($ref_self_url_path)-1)) {
+					Config::get(Config::SELF_URL_PATH) != $ref_self_url_path && Config::get(Config::SELF_URL_PATH) != mb_substr($ref_self_url_path, 0, mb_strlen($ref_self_url_path)-1)) {
 					array_push($errors,
-						"Please set SELF_URL_PATH to the correct value detected for your server: <b>$ref_self_url_path</b> (you're using: <b>" . SELF_URL_PATH . "</b>)");
+						"Please set Config::get(Config::SELF_URL_PATH) to the correct value detected for your server: <b>$ref_self_url_path</b> (you're using: <b>" . Config::get(Config::SELF_URL_PATH) . "</b>)");
 				}
 			}
 
-			if (!is_writable(ICONS_DIR)) {
-				array_push($errors, "ICONS_DIR defined in config.php is not writable (chmod -R 777 ".ICONS_DIR.").\n");
+			if (!is_writable(Config::get(Config::ICONS_DIR))) {
+				array_push($errors, "ICONS_DIR defined in config.php is not writable (chmod -R 777 ".Config::get(Config::ICONS_DIR).").\n");
 			}
 
-			if (!is_writable(LOCK_DIRECTORY)) {
-				array_push($errors, "LOCK_DIRECTORY defined in config.php is not writable (chmod -R 777 ".LOCK_DIRECTORY.").\n");
+			if (!is_writable(Config::get(Config::LOCK_DIRECTORY))) {
+				array_push($errors, "Config::get(Config::LOCK_DIRECTORY) defined in config.php is not writable (chmod -R 777 ".Config::get(Config::LOCK_DIRECTORY).").\n");
 			}
 
 			if (!function_exists("curl_init") && !ini_get("allow_url_fopen")) {
@@ -161,7 +143,7 @@
 				array_push($errors, "PHP support for DOMDocument is required, but was not found.");
 			}
 
-			if (DB_TYPE == "mysql") {
+			if (Config::get(Config::DB_TYPE) == "mysql") {
 				$bad_tables = check_mysql_tables();
 
 				if (count($bad_tables) > 0) {
diff --git a/include/sanity_config.php b/include/sanity_config.php
deleted file mode 100644
index b304adf54..000000000
--- a/include/sanity_config.php
+++ /dev/null
@@ -1,3 +0,0 @@
-<?php # This file has been generated at:  Mon Feb 22 14:17:27 MSK 2021
-define('GENERATED_CONFIG_CHECK', 26);
-function get_required_defines() { return [ 'DB_TYPE', 'DB_HOST', 'DB_USER', 'DB_NAME', 'DB_PASS', 'MYSQL_CHARSET', 'SELF_URL_PATH', 'SINGLE_USER_MODE', 'SIMPLE_UPDATE_MODE', 'PHP_EXECUTABLE', 'LOCK_DIRECTORY', 'CACHE_DIR', 'ICONS_DIR', 'ICONS_URL', 'AUTH_AUTO_CREATE', 'AUTH_AUTO_LOGIN', 'FORCE_ARTICLE_PURGE', 'SESSION_COOKIE_LIFETIME', 'SMTP_FROM_NAME', 'SMTP_FROM_ADDRESS', 'DIGEST_SUBJECT', 'CHECK_FOR_UPDATES', 'PLUGINS', 'LOG_DESTINATION', 'CONFIG_VERSION']; }
diff --git a/include/sessions.php b/include/sessions.php
index 5b372612b..8b7de0ac7 100644
--- a/include/sessions.php
+++ b/include/sessions.php
@@ -3,12 +3,12 @@
 
 	// Original from http://www.daniweb.com/code/snippet43.html
 
-	require_once "config.php";
 	require_once "autoload.php";
+	require_once "functions.php";
 	require_once "errorhandler.php";
 	require_once "lib/gettext/gettext.inc.php";
 
-	$session_expire = min(2147483647 - time() - 1, max(SESSION_COOKIE_LIFETIME, 86400));
+	$session_expire = min(2147483647 - time() - 1, max(\Config::get(\Config::SESSION_COOKIE_LIFETIME), 86400));
 	$session_name = (!defined('TTRSS_SESSION_NAME')) ? "ttrss_sid" : TTRSS_SESSION_NAME;
 
 	if (is_server_https()) {
@@ -37,7 +37,7 @@
 	}
 
 	function validate_session() {
-		if (SINGLE_USER_MODE) return true;
+		if (\Config::get(\Config::SINGLE_USER_MODE)) return true;
 
 		if (isset($_SESSION["ref_schema_version"]) && $_SESSION["ref_schema_version"] != session_get_schema_version()) {
 			$_SESSION["login_error_msg"] =
@@ -144,7 +144,7 @@
 		return true;
 	}
 
-	if (!SINGLE_USER_MODE /* && DB_TYPE == "pgsql" */) {
+	if (!\Config::get(\Config::SINGLE_USER_MODE)) {
 		session_set_save_handler('\Sessions\ttrss_open',
 			'\Sessions\ttrss_close', '\Sessions\ttrss_read',
 			'\Sessions\ttrss_write', '\Sessions\ttrss_destroy',
diff --git a/index.php b/index.php
index eec54c55b..1f2802864 100644
--- a/index.php
+++ b/index.php
@@ -1,9 +1,4 @@
 <?php
-	if (!file_exists("config.php")) {
-		print "<b>Fatal Error</b>: You forgot to copy
-		<b>config.php-dist</b> to <b>config.php</b> and edit it.\n";
-		exit;
-	}
 
 	// we need a separate check here because functions.php might get parsed
 	// incorrectly before 5.3 because of :: syntax.
@@ -19,8 +14,6 @@
 	require_once "sessions.php";
 	require_once "functions.php";
 	require_once "sanity_check.php";
-	require_once "config.php";
-	require_once "db-prefs.php";
 
 	if (!init_plugins()) return;
 
@@ -42,8 +35,8 @@
 		}
 	} ?>
 
-	<?php if (theme_exists(LOCAL_OVERRIDE_STYLESHEET)) {
-		echo stylesheet_tag(get_theme_path(LOCAL_OVERRIDE_STYLESHEET));
+	<?php if (theme_exists(Config::get(Config::LOCAL_OVERRIDE_STYLESHEET))) {
+		echo stylesheet_tag(get_theme_path(Config::get(Config::LOCAL_OVERRIDE_STYLESHEET)));
 	} ?>
 
 	<script type="text/javascript">
diff --git a/phpstan.neon b/phpstan.neon
index b2cd978d8..29ca27d26 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,7 +1,8 @@
 parameters:
    level: 5
    ignoreErrors:
-      - '#Constant.*not found#'
+#      - '#Constant.*not found#'
+      - '#Constant.*\b(SUBSTRING_FOR_DATE|SCHEMA_VERSION|SELF_USER_AGENT|LABEL_BASE_INDEX|PLUGIN_FEED_BASE_INDEX)\b.*not found#'
       - '#Comparison operation ">" between int<1, max> and 0 is always true.#'
       - '#Access to an undefined property DOMNode::\$tagName.#'
       - '#Call to an undefined method DOMNode::(get|remove|set)Attribute\(\).#'
diff --git a/plugins/af_proxy_http/init.php b/plugins/af_proxy_http/init.php
index a5ba1d62d..b03cacfe4 100644
--- a/plugins/af_proxy_http/init.php
+++ b/plugins/af_proxy_http/init.php
@@ -68,7 +68,7 @@ class Af_Proxy_Http extends Plugin {
 			header("Location: " . $this->cache->get_url($local_filename));
 			return;
 		} else {
-			$data = UrlHelper::fetch(["url" => $url, "max_size" => MAX_CACHE_FILE_SIZE]);
+			$data = UrlHelper::fetch(["url" => $url, "max_size" => Config::get(Config::MAX_CACHE_FILE_SIZE)]);
 
 			if ($data) {
 				if ($this->cache->put($local_filename, $data)) {
diff --git a/plugins/af_psql_trgm/init.php b/plugins/af_psql_trgm/init.php
index 3b7ed6b14..5611d8998 100644
--- a/plugins/af_psql_trgm/init.php
+++ b/plugins/af_psql_trgm/init.php
@@ -134,7 +134,7 @@ class Af_Psql_Trgm extends Plugin {
 			title="<i class='material-icons'>extension</i> <?= __('Mark similar articles as read (af_psql_trgm)') ?>">
 
 			<?php
-			if (DB_TYPE != "pgsql") {
+			if (Config::get(Config::DB_TYPE) != "pgsql") {
 				print_error("Database type not supported.");
 			} else {
 				$res = $this->pdo->query("select 'similarity'::regproc");
@@ -258,7 +258,7 @@ class Af_Psql_Trgm extends Plugin {
 
 	function hook_article_filter($article) {
 
-		if (DB_TYPE != "pgsql") return $article;
+		if (Config::get(Config::DB_TYPE) != "pgsql") return $article;
 
 		$res = $this->pdo->query("select 'similarity'::regproc");
 		if (!$res || !$res->fetch()) return $article;
diff --git a/plugins/af_redditimgur/init.php b/plugins/af_redditimgur/init.php
index 9e43b255f..7d5aeff5a 100755
--- a/plugins/af_redditimgur/init.php
+++ b/plugins/af_redditimgur/init.php
@@ -530,7 +530,7 @@ class Af_RedditImgur extends Plugin {
 						$entry_guid = $article["guid_hashed"];
 						$owner_uid = $article["owner_uid"];
 
-						if (DB_TYPE == "pgsql") {
+						if (Config::get(Config::DB_TYPE) == "pgsql") {
 							$interval_qpart = "date_entered < NOW() - INTERVAL '1 day'";
 						} else {
 							$interval_qpart = "date_entered < DATE_SUB(NOW(), INTERVAL 1 DAY)";
diff --git a/plugins/auth_internal/init.php b/plugins/auth_internal/init.php
index 6a68534ea..13a7bc969 100644
--- a/plugins/auth_internal/init.php
+++ b/plugins/auth_internal/init.php
@@ -244,7 +244,7 @@ class Auth_Internal extends Auth_Base {
 				$tpl->readTemplateFromFile("password_change_template.txt");
 
 				$tpl->setVariable('LOGIN', $row["login"]);
-				$tpl->setVariable('TTRSS_HOST', SELF_URL_PATH);
+				$tpl->setVariable('TTRSS_HOST', Config::get(Config::SELF_URL_PATH));
 
 				$tpl->addBlock('message');
 
diff --git a/plugins/bookmarklets/init.php b/plugins/bookmarklets/init.php
index caa8b39df..967918823 100644
--- a/plugins/bookmarklets/init.php
+++ b/plugins/bookmarklets/init.php
@@ -21,7 +21,7 @@ class Bookmarklets extends Plugin {
 	}
 
 	function subscribe() {
-		if (SINGLE_USER_MODE) {
+		if (Config::get(Config::SINGLE_USER_MODE)) {
 			UserHelper::login_sequence();
 		}
 
@@ -172,7 +172,7 @@ class Bookmarklets extends Plugin {
 	}
 
 	function sharepopup() {
-		if (SINGLE_USER_MODE) {
+		if (Config::get(Config::SINGLE_USER_MODE)) {
 			UserHelper::login_sequence();
 		}
 
diff --git a/plugins/cache_starred_images/init.php b/plugins/cache_starred_images/init.php
index 9f17c492f..2dbdb99cc 100755
--- a/plugins/cache_starred_images/init.php
+++ b/plugins/cache_starred_images/init.php
@@ -136,7 +136,7 @@ class Cache_Starred_Images extends Plugin {
 		if (!$this->cache->exists($local_filename)) {
 			Debug::log("cache_images: downloading: $url to $local_filename", Debug::$LOG_VERBOSE);
 
-			$data = UrlHelper::fetch(["url" => $url, "max_size" => MAX_CACHE_FILE_SIZE]);
+			$data = UrlHelper::fetch(["url" => $url, "max_size" => Config::get(Config::MAX_CACHE_FILE_SIZE)]);
 
 			if ($data)
 				return $this->cache->put($local_filename, $data);;
diff --git a/prefs.php b/prefs.php
index f173d684b..851dd898a 100644
--- a/prefs.php
+++ b/prefs.php
@@ -2,18 +2,10 @@
 	set_include_path(__DIR__ ."/include" . PATH_SEPARATOR .
 		get_include_path());
 
-	if (!file_exists("config.php")) {
-		print "<b>Fatal Error</b>: You forgot to copy
-		<b>config.php-dist</b> to <b>config.php</b> and edit it.\n";
-		exit;
-	}
-
 	require_once "autoload.php";
 	require_once "sessions.php";
 	require_once "functions.php";
 	require_once "sanity_check.php";
-	require_once "config.php";
-	require_once "db-prefs.php";
 
 	if (!init_plugins()) return;
 
@@ -34,8 +26,8 @@
 		}
 	} ?>
 
-	<?php if (theme_exists(LOCAL_OVERRIDE_STYLESHEET)) {
-		echo stylesheet_tag(get_theme_path(LOCAL_OVERRIDE_STYLESHEET));
+	<?php if (theme_exists(Config::get(Config::LOCAL_OVERRIDE_STYLESHEET))) {
+		echo stylesheet_tag(get_theme_path(Config::get(Config::LOCAL_OVERRIDE_STYLESHEET)));
 	} ?>
 
 	<script type="text/javascript">
diff --git a/public.php b/public.php
index 48fe675f8..43aa66c1d 100644
--- a/public.php
+++ b/public.php
@@ -6,8 +6,6 @@
 	require_once "sessions.php";
 	require_once "functions.php";
 	require_once "sanity_check.php";
-	require_once "config.php";
-	require_once "db-prefs.php";
 
 	startup_gettext();
 
diff --git a/update.php b/update.php
index ab6272c83..8d8566db7 100755
--- a/update.php
+++ b/update.php
@@ -9,12 +9,10 @@
 
 	require_once "autoload.php";
 	require_once "functions.php";
-	require_once "config.php";
 	require_once "sanity_check.php";
-	require_once "db-prefs.php";
 
 	function make_stampfile($filename) {
-		$fp = fopen(LOCK_DIRECTORY . "/$filename", "w");
+		$fp = fopen(Config::get(Config::LOCK_DIRECTORY) . "/$filename", "w");
 
 		if (flock($fp, LOCK_EX | LOCK_NB)) {
 			fwrite($fp, time() . "\n");
@@ -30,9 +28,9 @@
 
 		$days = (int) $days;
 
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$interval_query = "date_updated < NOW() - INTERVAL '$days days'";
-		} else /*if (DB_TYPE == "mysql") */ {
+		} else /*if (Config::get(Config::DB_TYPE) == "mysql") */ {
 			$interval_query = "date_updated < DATE_SUB(NOW(), INTERVAL $days DAY)";
 		}
 
@@ -212,7 +210,7 @@
 	}
 
 	if (isset($options["feeds"])) {
-		RSSUtils::update_daemon_common(DAEMON_FEED_LIMIT, $options);
+		RSSUtils::update_daemon_common(Config::get(Config::DAEMON_FEED_LIMIT), $options);
 		RSSUtils::housekeeping_common();
 
 		PluginHost::getInstance()->run_hooks(PluginHost::HOOK_UPDATE_TASK, $options);
@@ -224,10 +222,10 @@
 			$log = isset($options['log']) ? '--log '.$options['log'] : '';
 			$log_level = isset($options['log-level']) ? '--log-level '.$options['log-level'] : '';
 
-			passthru(PHP_EXECUTABLE . " " . $argv[0] ." --daemon-loop $quiet $log $log_level");
+			passthru(Config::get(Config::PHP_EXECUTABLE) . " " . $argv[0] ." --daemon-loop $quiet $log $log_level");
 
 			// let's enforce a minimum spawn interval as to not forkbomb the host
-			$spawn_interval = max(60, DAEMON_SLEEP_INTERVAL);
+			$spawn_interval = max(60, Config::get(Config::DAEMON_SLEEP_INTERVAL));
 
 			Debug::log("Sleeping for $spawn_interval seconds...");
 			sleep($spawn_interval);
@@ -255,7 +253,7 @@
 			Debug::log("warning: unable to create stampfile\n");
 		}
 
-		RSSUtils::update_daemon_common(isset($options["pidlock"]) ? 50 : DAEMON_FEED_LIMIT, $options);
+		RSSUtils::update_daemon_common(isset($options["pidlock"]) ? 50 : Config::get(Config::DAEMON_FEED_LIMIT), $options);
 
 		if (!isset($options["pidlock"]) || $options["task"] == 0)
 			RSSUtils::housekeeping_common();
@@ -277,7 +275,7 @@
 
 		Debug::log("clearing existing indexes...");
 
-		if (DB_TYPE == "pgsql") {
+		if (Config::get(Config::DB_TYPE) == "pgsql") {
 			$sth = $pdo->query( "SELECT relname FROM
 				pg_catalog.pg_class WHERE relname LIKE 'ttrss_%'
 					AND relname NOT LIKE '%_pkey'
@@ -288,7 +286,7 @@
 		}
 
 		while ($line = $sth->fetch()) {
-			if (DB_TYPE == "pgsql") {
+			if (Config::get(Config::DB_TYPE) == "pgsql") {
 				$statement = "DROP INDEX " . $line["relname"];
 				Debug::log($statement);
 			} else {
@@ -299,9 +297,9 @@
 			$pdo->query($statement);
 		}
 
-		Debug::log("reading indexes from schema for: " . DB_TYPE);
+		Debug::log("reading indexes from schema for: " . Config::get(Config::DB_TYPE));
 
-		$fp = fopen("schema/ttrss_schema_" . DB_TYPE . ".sql", "r");
+		$fp = fopen("schema/ttrss_schema_" . Config::get(Config::DB_TYPE) . ".sql", "r");
 		if ($fp) {
 			while ($line = fgets($fp)) {
 				$matches = array();
@@ -375,14 +373,14 @@
 	}
 
 	if (isset($options["update-schema"])) {
-		Debug::log("Checking for updates (" . DB_TYPE . ")...");
+		Debug::log("Checking for updates (" . Config::get(Config::DB_TYPE) . ")...");
 
-		$updater = new DbUpdater(Db::pdo(), DB_TYPE, SCHEMA_VERSION);
+		$updater = new DbUpdater(Db::pdo(), Config::get(Config::DB_TYPE), SCHEMA_VERSION);
 
 		if ($updater->is_update_required()) {
 			Debug::log("Schema update required, version " . $updater->get_schema_version() . " to " . SCHEMA_VERSION);
 
-			if (DB_TYPE == "mysql")
+			if (Config::get(Config::DB_TYPE) == "mysql")
 				Debug::Log("READ THIS: Due to MySQL limitations, your database is not completely protected while updating.\n".
 					"Errors may put it in an inconsistent state requiring manual rollback.\nBACKUP YOUR DATABASE BEFORE CONTINUING.");
 			else
@@ -460,7 +458,7 @@
 	if (isset($options["list-plugins"])) {
 		$tmppluginhost = new PluginHost();
 		$tmppluginhost->load_all($tmppluginhost::KIND_ALL);
-		$enabled = array_map("trim", explode(",", PLUGINS));
+		$enabled = array_map("trim", explode(",", Config::get(Config::PLUGINS)));
 
 		echo "List of all available plugins:\n";
 
@@ -515,8 +513,8 @@
 
 	PluginHost::getInstance()->run_commands($options);
 
-	if (file_exists(LOCK_DIRECTORY . "/$lock_filename"))
+	if (file_exists(Config::get(Config::LOCK_DIRECTORY) . "/$lock_filename"))
 		if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN')
 			fclose($lock_handle);
-		unlink(LOCK_DIRECTORY . "/$lock_filename");
+		unlink(Config::get(Config::LOCK_DIRECTORY) . "/$lock_filename");
 ?>
diff --git a/update_daemon2.php b/update_daemon2.php
index 5d4d3759c..b75f06ae5 100755
--- a/update_daemon2.php
+++ b/update_daemon2.php
@@ -10,16 +10,7 @@
 
 	require_once "autoload.php";
 	require_once "functions.php";
-	require_once "config.php";
-
-	// defaults
-	if (!defined('PURGE_INTERVAL')) 						define('PURGE_INTERVAL', 3600); // seconds
-	if (!defined('MAX_CHILD_RUNTIME')) 					define('MAX_CHILD_RUNTIME', 1800); // seconds
-	if (!defined('MAX_JOBS')) 								define('MAX_JOBS', 2);
-	if (!defined('SPAWN_INTERVAL')) 						define('SPAWN_INTERVAL', DAEMON_SLEEP_INTERVAL); // seconds
-
 	require_once "sanity_check.php";
-	require_once "db-prefs.php";
 
 	if (!function_exists('pcntl_fork')) {
 		die("error: This script requires PHP compiled with PCNTL module.\n");
@@ -78,7 +69,7 @@
 		foreach (array_keys($ctimes) as $pid) {
 			$started = $ctimes[$pid];
 
-			if (time() - $started > MAX_CHILD_RUNTIME) {
+			if (time() - $started > Config::get(Config::DAEMON_MAX_CHILD_RUNTIME)) {
 				Debug::log("Child process with PID $pid seems to be stuck, aborting...");
 				posix_kill($pid, SIGKILL);
 			}
@@ -98,9 +89,9 @@
 
 	function shutdown($caller_pid) {
 		if ($caller_pid == posix_getpid()) {
-			if (file_exists(LOCK_DIRECTORY . "/update_daemon.lock")) {
+			if (file_exists(Config::get(Config::LOCK_DIRECTORY) . "/update_daemon.lock")) {
 				Debug::log("Removing lockfile (master)...");
-				unlink(LOCK_DIRECTORY . "/update_daemon.lock");
+				unlink(Config::get(Config::LOCK_DIRECTORY) . "/update_daemon.lock");
 			}
 		}
 	}
@@ -108,9 +99,9 @@
 	function task_shutdown() {
 		$pid = posix_getpid();
 
-		if (file_exists(LOCK_DIRECTORY . "/update_daemon-$pid.lock")) {
+		if (file_exists(Config::get(Config::LOCK_DIRECTORY) . "/update_daemon-$pid.lock")) {
 			Debug::log("Removing task lockfile for PID $pid...");
-			unlink(LOCK_DIRECTORY . "/update_daemon-$pid.lock");
+			unlink(Config::get(Config::LOCK_DIRECTORY) . "/update_daemon-$pid.lock");
 		}
 	}
 
@@ -143,9 +134,9 @@
 		print "  --log FILE           - log messages to FILE\n";
         print "  --log-level N        - log verbosity level\n";
 		print "  --tasks N            - amount of update tasks to spawn\n";
-		print "                         default: " . MAX_JOBS . "\n";
+		print "                         default: " . Config::get(Config::DAEMON_MAX_JOBS) . "\n";
 		print "  --interval N         - task spawn interval\n";
-		print "                         default: " . SPAWN_INTERVAL . " seconds.\n";
+		print "                         default: " . Config::get(Config::DAEMON_SLEEP_INTERVAL) . " seconds.\n";
 		print "  --quiet              - don't output messages to stdout\n";
 		return;
 	}
@@ -170,14 +161,14 @@
 		Debug::log("Set to spawn " . $options["tasks"] . " children.");
 		$max_jobs = $options["tasks"];
 	} else {
-		$max_jobs = MAX_JOBS;
+		$max_jobs = Config::get(Config::DAEMON_MAX_JOBS);
 	}
 
 	if (isset($options["interval"])) {
 		Debug::log("Spawn interval: " . $options["interval"] . " seconds.");
 		$spawn_interval = $options["interval"];
 	} else {
-		$spawn_interval = SPAWN_INTERVAL;
+		$spawn_interval = Config::get(Config::DAEMON_SLEEP_INTERVAL);
 	}
 
 	// let's enforce a minimum spawn interval as to not forkbomb the host
@@ -249,7 +240,7 @@
 
 					$my_pid = posix_getpid();
 
-					passthru(PHP_EXECUTABLE . " update.php --daemon-loop $quiet $log --task $j --pidlock $my_pid");
+					passthru(Config::get(Config::PHP_EXECUTABLE) . " update.php --daemon-loop $quiet $log --task $j --pidlock $my_pid");
 
 					sleep(1);
 
diff --git a/utils/regen_config_checks.sh b/utils/regen_config_checks.sh
deleted file mode 100755
index b20ce0480..000000000
--- a/utils/regen_config_checks.sh
+++ /dev/null
@@ -1,17 +0,0 @@
-#!/bin/sh
-
-DESTINATION="include/sanity_config.php"
-
-echo "<?php # This file has been generated at: " `date` > $DESTINATION
-
-echo -n "define('GENERATED_CONFIG_CHECK', " >> $DESTINATION
-grep CONFIG_VERSION config.php-dist | awk -F ' |\)' '{ print $2 }' | xargs echo -n >> $DESTINATION
-echo ");" >> $DESTINATION
-
-echo -n "function get_required_defines() { return [ " >> $DESTINATION
-
-grep define\( config.php-dist | awk -F\' '{ print "*" $2 "*," }' | grep -v DB_PORT | xargs echo -n | sed -e s/,$// -e s/*/\'/g >> $DESTINATION
-
-echo "]; }" >> $DESTINATION
-
-