diff --git a/extension.json b/extension.json
index 7b78ecf6..0fa16d97 100644
--- a/extension.json
+++ b/extension.json
@@ -32,7 +32,7 @@
 	},
 	"HookHandlers": {
 		"main": {
-			"class": "UniversalLanguageSelectorHooks",
+			"class": "UniversalLanguageSelector\\Hooks",
 			"services": [
 				"MainConfig",
 				"UserOptionsLookup",
@@ -42,15 +42,15 @@
 		}
 	},
 	"APIModules": {
-		"languagesearch": "ApiLanguageSearch",
+		"languagesearch": "UniversalLanguageSelector\\Api\\ApiLanguageSearch",
 		"ulslocalization": {
-			"class": "ApiULSLocalization",
+			"class": "UniversalLanguageSelector\\Api\\ApiULSLocalization",
 			"services": [
 				"LanguageNameUtils"
 			]
 		},
 		"ulssetlang": {
-			"class": "ApiULSSetLanguage",
+			"class": "UniversalLanguageSelector\\Api\\ApiULSSetLanguage",
 			"services": [
 				"UserOptionsManager",
 				"LanguageNameUtils"
@@ -64,16 +64,11 @@
 		]
 	},
 	"AutoloadClasses": {
-		"ApiLanguageSearch": "includes/api/ApiLanguageSearch.php",
-		"ApiULSLocalization": "includes/api/ApiULSLocalization.php",
-		"ApiULSSetLanguage": "includes/api/ApiULSSetLanguage.php",
-		"FontRepoCompiler": "includes/FontRepoCompiler.php",
 		"LanguageNameSearch": "data/LanguageNameSearch.php",
-		"LanguageNameSearchData": "data/LanguageNameSearchData.php",
-		"ResourceLoaderULSJsonMessageModule": "includes/ResourceLoaderULSJsonMessageModule.php",
-		"ResourceLoaderULSModule": "includes/ResourceLoaderULSModule.php",
-		"ULSJsonMessageLoader": "includes/ULSJsonMessageLoader.php",
-		"UniversalLanguageSelectorHooks": "includes/UniversalLanguageSelectorHooks.php"
+		"LanguageNameSearchData": "data/LanguageNameSearchData.php"
+	},
+	"AutoloadNamespaces": {
+		"UniversalLanguageSelector\\": "includes/"
 	},
 	"DefaultUserOptions": {
 		"uls-preferences": "",
@@ -146,7 +141,7 @@
 			"value": false
 		}
 	},
-	"callback": "UniversalLanguageSelectorHooks::setVersionConstant",
+	"callback": "UniversalLanguageSelector\\Hooks::setVersionConstant",
 	"ResourceFileModulePaths": {
 		"localBasePath": "resources",
 		"remoteExtPath": "UniversalLanguageSelector/resources"
@@ -267,7 +262,7 @@
 			"styles": "css/ext.uls.interlanguage.less"
 		},
 		"ext.uls.languagenames": {
-			"class": "ResourceLoaderULSModule"
+			"class": "UniversalLanguageSelector\\ResourceLoaderULSModule"
 		},
 		"ext.uls.languagesettings": {
 			"scripts": "js/ext.uls.languagesettings.js",
@@ -296,7 +291,7 @@
 			]
 		},
 		"ext.uls.messages": {
-			"class": "ResourceLoaderULSJsonMessageModule",
+			"class": "UniversalLanguageSelector\\ResourceLoaderULSJsonMessageModule",
 			"dependencies": "ext.uls.i18n"
 		},
 		"ext.uls.preferences": {
diff --git a/includes/api/ApiLanguageSearch.php b/includes/Api/ApiLanguageSearch.php
similarity index 95%
rename from includes/api/ApiLanguageSearch.php
rename to includes/Api/ApiLanguageSearch.php
index f9a16bdb..f2487582 100644
--- a/includes/api/ApiLanguageSearch.php
+++ b/includes/Api/ApiLanguageSearch.php
@@ -18,6 +18,10 @@
  * @license MIT
  */
 
+namespace UniversalLanguageSelector\Api;
+
+use ApiBase;
+use LanguageNameSearch;
 use Wikimedia\ParamValidator\ParamValidator;
 
 /**
diff --git a/includes/api/ApiULSLocalization.php b/includes/Api/ApiULSLocalization.php
similarity index 94%
rename from includes/api/ApiULSLocalization.php
rename to includes/Api/ApiULSLocalization.php
index f09d7dda..7eb3483b 100644
--- a/includes/api/ApiULSLocalization.php
+++ b/includes/Api/ApiULSLocalization.php
@@ -18,7 +18,13 @@
  * @license MIT
  */
 
+namespace UniversalLanguageSelector\Api;
+
+use ApiBase;
+use ApiFormatRaw;
+use ApiMain;
 use MediaWiki\Languages\LanguageNameUtils;
+use UniversalLanguageSelector\ULSJsonMessageLoader;
 use Wikimedia\ParamValidator\ParamValidator;
 
 /**
diff --git a/includes/api/ApiULSSetLanguage.php b/includes/Api/ApiULSSetLanguage.php
similarity index 97%
rename from includes/api/ApiULSSetLanguage.php
rename to includes/Api/ApiULSSetLanguage.php
index 2654d089..18a5cc06 100644
--- a/includes/api/ApiULSSetLanguage.php
+++ b/includes/Api/ApiULSSetLanguage.php
@@ -18,6 +18,11 @@
  * @license MIT
  */
 
+namespace UniversalLanguageSelector\Api;
+
+use ApiBase;
+use ApiMain;
+use DeferredUpdates;
 use MediaWiki\Languages\LanguageNameUtils;
 use MediaWiki\User\UserOptionsManager;
 use Wikimedia\ParamValidator\ParamValidator;
@@ -79,7 +84,6 @@ class ApiULSSetLanguage extends ApiBase {
 		}
 
 		$updateUser = $user->getInstanceForUpdate();
-		// @phan-suppress-next-line SecurityCheck-SQLInjection False positive caused by T290563
 		$this->userOptionsManager->setOption( $updateUser, 'language', $languageCode );
 		// Sync the DB on post-send
 		DeferredUpdates::addCallableUpdate( static function () use ( $updateUser ) {
diff --git a/includes/FontRepoCompiler.php b/includes/FontRepoCompiler.php
index 35d56fe8..a8f338b4 100644
--- a/includes/FontRepoCompiler.php
+++ b/includes/FontRepoCompiler.php
@@ -1,7 +1,12 @@
 <?php
 
+namespace UniversalLanguageSelector;
+
+use OutputPage;
+
 /**
  * This class parses font specification ini files to a central list.
+ *
  * @author Niklas Laxström
  * @since 2016.04
  */
diff --git a/includes/UniversalLanguageSelectorHooks.php b/includes/Hooks.php
similarity index 98%
rename from includes/UniversalLanguageSelectorHooks.php
rename to includes/Hooks.php
index c4f6fee3..15644c8c 100644
--- a/includes/UniversalLanguageSelectorHooks.php
+++ b/includes/Hooks.php
@@ -18,6 +18,14 @@
  * @license MIT
  */
 
+namespace UniversalLanguageSelector;
+
+use Babel;
+use Config;
+use ExtensionRegistry;
+use Html;
+use IBufferingStatsdDataFactory;
+use IContextSource;
 use MediaWiki\Extension\BetaFeatures\BetaFeatures;
 use MediaWiki\Hook\BeforePageDisplayHook;
 use MediaWiki\Hook\MakeGlobalVariablesScriptHook;
@@ -28,11 +36,18 @@ use MediaWiki\Preferences\Hook\GetPreferencesHook;
 use MediaWiki\ResourceLoader\Hook\ResourceLoaderGetConfigVarsHook;
 use MediaWiki\Skins\Hook\SkinAfterPortletHook;
 use MediaWiki\User\UserOptionsLookup;
+use MobileContext;
+use OutputPage;
+use RequestContext;
+use Skin;
+use SkinTemplate;
+use Title;
+use User;
 
 /**
  * @phpcs:disable MediaWiki.NamingConventions.LowerCamelFunctionsName.FunctionName
  */
-class UniversalLanguageSelectorHooks implements
+class Hooks implements
 	BeforePageDisplayHook,
 	PersonalUrlsHook,
 	UserGetLanguageObjectHook,
@@ -84,7 +99,7 @@ class UniversalLanguageSelectorHooks implements
 		// this button. Using the SkinTemplateNavigation::Universal hook will ensure the button is
 		// added to the correct menu.
 		if ( version_compare( MW_VERSION, '1.37', '<' ) ) {
-			$wgHooks['PersonalUrls'][] = "UniversalLanguageSelectorHooks::onPersonalUrls";
+			$wgHooks['PersonalUrls'][] = "UniversalLanguageSelector\\Hooks::onPersonalUrls";
 		}
 	}
 
diff --git a/includes/ResourceLoaderULSJsonMessageModule.php b/includes/ResourceLoaderULSJsonMessageModule.php
index c093f91b..c5ecc172 100644
--- a/includes/ResourceLoaderULSJsonMessageModule.php
+++ b/includes/ResourceLoaderULSJsonMessageModule.php
@@ -7,6 +7,12 @@
  * @author Santhosh Thottingal
  */
 
+namespace UniversalLanguageSelector;
+
+use ResourceLoaderContext;
+use ResourceLoaderModule;
+use Xml;
+
 /**
  * ResourceLoader module for client-side loading of json-based localization.
  */
diff --git a/includes/ResourceLoaderULSModule.php b/includes/ResourceLoaderULSModule.php
index e2465439..e5ed6f15 100644
--- a/includes/ResourceLoaderULSModule.php
+++ b/includes/ResourceLoaderULSModule.php
@@ -19,6 +19,13 @@
  * @license MIT
  */
 
+namespace UniversalLanguageSelector;
+
+use Language;
+use ResourceLoader;
+use ResourceLoaderContext;
+use ResourceLoaderModule;
+
 /**
  * ResourceLoader module for UniversalLanguageSelector
  */
diff --git a/includes/ULSJsonMessageLoader.php b/includes/ULSJsonMessageLoader.php
index 876bbe15..8880f004 100644
--- a/includes/ULSJsonMessageLoader.php
+++ b/includes/ULSJsonMessageLoader.php
@@ -19,6 +19,10 @@
  * @since 2013.11
  */
 
+namespace UniversalLanguageSelector;
+
+use Language;
+
 class ULSJsonMessageLoader {
 	/**
 	 * Returns all message files that are used to load messages for the given
diff --git a/tests/phpunit/FontRepoCompilerTest.php b/tests/phpunit/FontRepoCompilerTest.php
index 68877c0b..ff27c0eb 100644
--- a/tests/phpunit/FontRepoCompilerTest.php
+++ b/tests/phpunit/FontRepoCompilerTest.php
@@ -2,10 +2,10 @@
 
 namespace UniversalLanguageSelector\Tests;
 
-use FontRepoCompiler;
+use UniversalLanguageSelector\FontRepoCompiler;
 
 /**
- * @covers \FontRepoCompiler
+ * @covers \UniversalLanguageSelector\FontRepoCompiler
  *
  * @license GPL-2.0-or-later
  * @author Thiemo Kreuz
diff --git a/tests/phpunit/ResourceLoaderULSJsonMessageModuleTest.php b/tests/phpunit/ResourceLoaderULSJsonMessageModuleTest.php
index 045c6bb1..5ef90202 100644
--- a/tests/phpunit/ResourceLoaderULSJsonMessageModuleTest.php
+++ b/tests/phpunit/ResourceLoaderULSJsonMessageModuleTest.php
@@ -2,10 +2,10 @@
 
 namespace UniversalLanguageSelector\Tests;
 
-use ResourceLoaderULSJsonMessageModule;
+use UniversalLanguageSelector\ResourceLoaderULSJsonMessageModule;
 
 /**
- * @covers \ResourceLoaderULSJsonMessageModule
+ * @covers \UniversalLanguageSelector\ResourceLoaderULSJsonMessageModule
  *
  * @license GPL-2.0-or-later
  * @author Thiemo Kreuz
diff --git a/tests/phpunit/ResourceLoaderULSModuleTest.php b/tests/phpunit/ResourceLoaderULSModuleTest.php
index b8853589..832c49cb 100644
--- a/tests/phpunit/ResourceLoaderULSModuleTest.php
+++ b/tests/phpunit/ResourceLoaderULSModuleTest.php
@@ -2,10 +2,10 @@
 
 namespace UniversalLanguageSelector\Tests;
 
-use ResourceLoaderULSModule;
+use UniversalLanguageSelector\ResourceLoaderULSModule;
 
 /**
- * @covers \ResourceLoaderULSModule
+ * @covers \UniversalLanguageSelector\ResourceLoaderULSModule
  *
  * @license GPL-2.0-or-later
  * @author Thiemo Kreuz
diff --git a/tests/phpunit/ULSJsonMessageLoaderTest.php b/tests/phpunit/ULSJsonMessageLoaderTest.php
index 9d5d14c3..70399107 100644
--- a/tests/phpunit/ULSJsonMessageLoaderTest.php
+++ b/tests/phpunit/ULSJsonMessageLoaderTest.php
@@ -2,10 +2,10 @@
 
 namespace UniversalLanguageSelector\Tests;
 
-use ULSJsonMessageLoader;
+use UniversalLanguageSelector\ULSJsonMessageLoader;
 
 /**
- * @covers \ULSJsonMessageLoader
+ * @covers \UniversalLanguageSelector\ULSJsonMessageLoader
  *
  * @license GPL-2.0-or-later
  * @author Thiemo Kreuz