diff --git a/.gitreview b/.gitreview
new file mode 100644
index 0000000..a20e8b0
--- /dev/null
+++ b/.gitreview
@@ -0,0 +1,6 @@
+[gerrit]
+host=gerrit.wikimedia.org
+port=29418
+project=mediawiki/extensions/Cognate.git
+defaultbranch=master
+defaultrebase=0
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..1e542f9
--- /dev/null
+++ b/README.md
@@ -0,0 +1,2 @@
+# InterwikiSorting extension
+EDIT
\ No newline at end of file
diff --git a/extension.json b/extension.json
new file mode 100644
index 0000000..2b97fd8
--- /dev/null
+++ b/extension.json
@@ -0,0 +1,33 @@
+{
+  "name": "InterwikiSorting",
+  "version": "0.0.1",
+  "author": [
+    "WMDE"
+  ],
+  "url": "https://www.mediawiki.org/wiki/Extension:InterwikiSorting",
+  "descriptionmsg": "interwikisorting-desc",
+  "license-name": "GPL-2.0+",
+  "type": "other",
+  "config": {
+    "InterwikiSortingNamespaces": [],
+    "InterwikiSortingAlwaysSort": false,
+    "InterwikiSortingSort": "code",
+    "InterwikiSortingSortPrepend": [],
+    "InterwikiSortingInterwikiSortOrders": []
+  },
+  "AutoloadClasses": {
+    "InterwikiSorting\\InterwikiSorter": "src/InterwikiSorter.php",
+    "InterwikiSorting\\InterwikiSortingHooks": "src/InterwikiSortingHooks.php",
+    "InterwikiSorting\\InterwikiSortingHookHandlers": "src/InterwikiSortingHookHandlers.php"
+  },
+  "Hooks": {
+    "BeforeInitialize": [ "InterwikiSorting\\InterwikiSortingHooks::onBeforeInitialize" ],
+    "UnitTestsList": [ "InterwikiSorting\\InterwikiSortingHooks::onUnitTestsList" ]
+  },
+  "MessagesDirs": {
+    "InterwikiSorting": [
+      "i18n"
+    ]
+  },
+  "manifest_version": 1
+}
\ No newline at end of file
diff --git a/i18n/en.json b/i18n/en.json
new file mode 100644
index 0000000..1264bf0
--- /dev/null
+++ b/i18n/en.json
@@ -0,0 +1,8 @@
+{
+  "@metadata": {
+    "authors": [
+      "Addshore"
+    ]
+  },
+  "interwikisorting-desc": "Sort interwiki links."
+}
\ No newline at end of file
diff --git a/i18n/qqq.json b/i18n/qqq.json
new file mode 100644
index 0000000..158978c
--- /dev/null
+++ b/i18n/qqq.json
@@ -0,0 +1,8 @@
+{
+	"@metadata": {
+		"authors": [
+			"Addshore"
+		]
+	},
+	"interwikisorting-desc": "{{desc|name=Cognate|url=https://www.mediawiki.org/wiki/Extension:InterwikiSorting}}"
+}
diff --git a/src/InterwikiSorter.php b/src/InterwikiSorter.php
new file mode 100644
index 0000000..02ced82
--- /dev/null
+++ b/src/InterwikiSorter.php
@@ -0,0 +1,142 @@
+<?php
+
+namespace InterwikiSorting;
+
+/**
+ * Language sorting utility functions.
+ *
+ * @license GPL-2.0+
+ * @author Nikola Smolenski <smolensk@eunet.rs>
+ * @author Katie Filbert < aude.wiki@gmail.com >
+ * @author Thiemo Mättig
+ */
+class InterwikiSorter {
+
+	/**
+	 * @see Documentation of "sort" and "interwikiSortOrders" options in docs/options.wiki.
+	 */
+	const SORT_CODE = 'code';
+
+	/**
+	 * @var array[]
+	 */
+	private $sortOrders;
+
+	/**
+	 * @var string
+	 */
+	private $sort;
+
+	/**
+	 * @var string[]
+	 */
+	private $sortPrepend;
+
+	/**
+	 * @var int[]|null
+	 */
+	private $sortOrder = null;
+
+	/**
+	 * @param string $sort
+	 * @param array[] $sortOrders
+	 * @param string[] $sortPrepend
+	 */
+	public function __construct( $sort, array $sortOrders = array(), array $sortPrepend = array() ) {
+		$this->sort = $sort;
+		$this->sortOrders = $sortOrders;
+		$this->sortPrepend = $sortPrepend;
+	}
+
+	/**
+	 * Sort an array of links in-place
+	 * @version Copied from InterlanguageExtension rev 114818
+	 *
+	 * @param string[] $links
+	 *
+	 * @return string[]
+	 */
+	public function sortLinks( array $links ) {
+		if ( $this->sortOrder === null ) {
+			$this->sortOrder = $this->buildSortOrder( $this->sort, $this->sortOrders );
+		}
+
+		// Prepare the array for sorting.
+		foreach ( $links as $k => $langLink ) {
+			$links[$k] = explode( ':', $langLink, 2 );
+		}
+
+		usort( $links, array( $this, 'compareLinks' ) );
+
+		// Restore the sorted array.
+		foreach ( $links as $k => $langLink ) {
+			$links[$k] = implode( ':', $langLink );
+		}
+
+		return $links;
+	}
+
+	/**
+	 * usort() callback function, compares the links on the basis of $sortOrder
+	 *
+	 * @param string[] $a
+	 * @param string[] $b
+	 *
+	 * @return int
+	 */
+	private function compareLinks( array $a, array $b ) {
+		$a = $a[0];
+		$b = $b[0];
+
+		if ( $a === $b ) {
+			return 0;
+		}
+
+		$aIndex = array_key_exists( $a, $this->sortOrder ) ? $this->sortOrder[$a] : null;
+		$bIndex = array_key_exists( $b, $this->sortOrder ) ? $this->sortOrder[$b] : null;
+
+		if ( $aIndex === $bIndex ) {
+			// If we encounter multiple unknown languages, which may happen if the sort table is not
+			// updated, we list them alphabetically.
+			return strcmp( $a, $b );
+		} elseif ( $aIndex === null ) {
+			// Unknown languages must go under the known languages.
+			return 1;
+		} elseif ( $bIndex === null ) {
+			return -1;
+		} else {
+			return $aIndex - $bIndex;
+		}
+	}
+
+	/**
+	 * Build sort order to be used by compareLinks().
+	 *
+	 * @param string $sort
+	 * @param array[] $sortOrders
+	 *
+	 * @return int[]
+	 */
+	private function buildSortOrder( $sort, array $sortOrders ) {
+		if ( $sort === self::SORT_CODE ) {
+			// The concept of known/unknown languages is irrelevant in strict code order.
+			$sortOrder = array();
+		} elseif ( !array_key_exists( $sort, $sortOrders ) ) {
+			// Something went wrong, but we can use default "code" order.
+			wfDebugLog(
+				__CLASS__,
+				__FUNCTION__ . ': Invalid or unknown sort order specified for interwiki links.'
+			);
+			$sortOrder = array();
+		} else {
+			$sortOrder = $sortOrders[$sort];
+		}
+
+		if ( $this->sortPrepend !== array() ) {
+			$sortOrder = array_unique( array_merge( $this->sortPrepend, $sortOrder ) );
+		}
+
+		return array_flip( $sortOrder );
+	}
+
+}
diff --git a/src/InterwikiSortingHookHandlers.php b/src/InterwikiSortingHookHandlers.php
new file mode 100644
index 0000000..069518f
--- /dev/null
+++ b/src/InterwikiSortingHookHandlers.php
@@ -0,0 +1,79 @@
+<?php
+
+namespace InterwikiSorting;
+
+use MediaWiki\MediaWikiServices;
+use ParserOutput;
+use Title;
+
+class ParserOutputUpdateHookHandlers {
+
+	/**
+	 * @var InterwikiSorter
+	 */
+	private $interwikiSorter;
+
+	/**
+	 * @var bool
+	 */
+	private $alwaysSort;
+
+	/**
+	 * @var int[]
+	 */
+	private $namespaces;
+
+	public static function newFromGlobalState() {
+		$config = MediaWikiServices::getInstance()->getMainConfig();
+
+		return new ParserOutputUpdateHookHandlers(
+			new InterwikiSorter(
+				$config->get( 'InterwikiSortingSort' ),
+				$config->get( 'InterwikiSortOrders' ),
+				$config->get( 'InterwikiSortingSortPrepend' )
+			),
+			$config->get( 'InterwikiSortingNamespaces' ),
+			$config->get( 'InterwikiSortingAlwaysSort' )
+		);
+	}
+
+	/**
+	 * @param InterwikiSorter $sorter
+	 * @param int[] $namespaces
+	 * @param boolean $alwaysSort
+	 */
+	public function __construct(
+		InterwikiSorter $sorter,
+		$namespaces,
+		$alwaysSort
+	) {
+		$this->interwikiSorter = $sorter;
+		$this->namespaces = $namespaces;
+		$this->alwaysSort = $alwaysSort;
+	}
+
+	/**
+	 * Hook runs after internal parsing
+	 * @see https://www.mediawiki.org/wiki/Manual:Hooks/ContentAlterParserOutput
+	 *
+	 * @param Title $title
+	 * @param ParserOutput $parserOutput
+	 *
+	 * @return bool
+	 */
+	public function doContentAlterParserOutput( Title $title, ParserOutput $parserOutput ) {
+		if ( !$title->inNamespaces( $this->namespaces ) ) {
+			// shorten out
+			return true;
+		}
+
+		if ( $this->alwaysSort ) {
+			$interwikiLinks = $parserOutput->getLanguageLinks();
+			$sortedLinks = $this->interwikiSorter->sortLinks( $interwikiLinks );
+			$parserOutput->setLanguageLinks( $sortedLinks );
+		}
+
+		return true;
+	}
+
+}
diff --git a/src/InterwikiSortingHooks.php b/src/InterwikiSortingHooks.php
new file mode 100644
index 0000000..07ac69f
--- /dev/null
+++ b/src/InterwikiSortingHooks.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace InterwikiSorting;
+
+use Content;
+use MediaWiki;
+use ParserOutput;
+use Title;
+
+class InterwikiSortingHooks {
+
+	/**
+	 * @param Content $content
+	 * @param Title $title
+	 * @param ParserOutput $parserOutput
+	 */
+	public static function onContentAlterParserOutput(
+		Content $content,
+		Title $title,
+		ParserOutput $parserOutput
+	) {
+		// this hook tries to access repo SiteLinkTable
+		// it interferes with any test that parses something, like a page or a message
+		if ( defined( 'MW_PHPUNIT_TEST' ) ) {
+			return;
+		}
+
+		$handler = ParserOutputUpdateHookHandlers::newFromGlobalState();
+		$handler->doContentAlterParserOutput( $title, $parserOutput );
+	}
+
+	public static function onBeforeInitialize(
+		/* Deliberately ignore all params ( We dont need them ) */
+	) {
+		global $wgHooks;
+		/**
+		 * The ContentAlterParserOutput hook is registered in the BeforeInitialize so that
+		 * the sorting of interwiki links is always done after anything else might change the
+		 * ParserOutput.
+		 * Hooks::register() can not be used due to the array_merge in Hooks::getHandlers()
+		 * which will return hooks in $wgHooks last.
+		 */
+		$wgHooks['ContentAlterParserOutput'][] =
+			array( InterwikiSortingHooks::class, 'onContentAlterParserOutput' );
+	}
+
+	public static function onUnitTestsList( &$files ) {
+		$files = array_merge( $files, __DIR__ . '/tests/phpunit' );
+		return true;
+	}
+
+}
diff --git a/tests/phpunit/InterwikiSorterTest.php b/tests/phpunit/InterwikiSorterTest.php
new file mode 100644
index 0000000..6a1e630
--- /dev/null
+++ b/tests/phpunit/InterwikiSorterTest.php
@@ -0,0 +1,134 @@
+<?php
+
+namespace InterwikiSorting\Tests;
+
+use InterwikiSorting\InterwikiSorter;
+
+/**
+ * @covers InterwikiSorting\InterwikiSorter
+ *
+ * @license GPL-2.0+
+ * @author Katie Filbert < aude.wiki@gmail.com >
+ */
+class InterwikiSorterTest extends \PHPUnit_Framework_TestCase {
+
+	public function sortOrdersProvider() {
+		return array(
+			'alphabetic' => array( 'ar', 'de', 'en', 'fr', 'ks', 'rn', 'ky', 'hu', 'ja', 'pt' ),
+			'alphabetic_revised' => array( 'ar', 'de', 'en', 'fr', 'ks', 'ky', 'rn', 'hu', 'ja', 'pt' ),
+			'alphabetic_sr' => array( 'ar', 'de', 'en', 'fr', 'ky', 'rn', 'ks', 'ja', 'hu', 'pt' ),
+			'mycustomorder' => array( 'de', 'ja', 'pt', 'hu', 'en' ),
+		);
+	}
+
+	public function constructorProvider() {
+		$sortOrders = $this->sortOrdersProvider();
+		return array(
+			array( 'code', $sortOrders, array() ),
+			array( 'code', $sortOrders, array( 'en' ) )
+		);
+	}
+
+	/**
+	 * @dataProvider constructorProvider
+	 */
+	public function testConstructor( $sort, $sortOrders, $sortPrepend ) {
+		$interwikiSorter = new InterwikiSorter( $sort, $sortOrders, $sortPrepend );
+		$this->assertInstanceOf( InterwikiSorter::class, $interwikiSorter );
+	}
+
+	public function sortLinksProvider() {
+		$sortOrders = $this->sortOrdersProvider();
+		$links = array( 'fr', 'ky', 'hu', 'ar', 'ks', 'ja', 'de', 'en', 'pt', 'rn' );
+
+		return array(
+			array(
+				$links, 'code', $sortOrders, array(),
+				array( 'ar', 'de', 'en', 'fr', 'hu', 'ja', 'ks', 'ky', 'pt', 'rn' )
+			),
+			array(
+				$links, 'code', $sortOrders, array( 'en' ),
+				array( 'en', 'ar', 'de', 'fr', 'hu', 'ja', 'ks', 'ky', 'pt', 'rn' )
+			),
+			array(
+				$links, 'alphabetic', $sortOrders, array(),
+				$sortOrders['alphabetic']
+			),
+			array(
+				$links, 'alphabetic', $sortOrders, array( 'en', 'ja' ),
+				array( 'en', 'ja', 'ar', 'de','fr', 'ks', 'rn', 'ky', 'hu', 'pt' )
+			),
+			array(
+				$links, 'alphabetic_revised', $sortOrders, array(),
+				$sortOrders['alphabetic_revised']
+			),
+			array(
+				$links, 'alphabetic_revised', $sortOrders, array( 'hu' ),
+				array( 'hu', 'ar', 'de', 'en', 'fr', 'ks', 'ky', 'rn', 'ja', 'pt' )
+			),
+			array(
+				array( 'ja', 'de', 'pt', 'en', 'hu' ), 'mycustomorder', $sortOrders, array(),
+				$sortOrders['mycustomorder']
+			),
+			array(
+				array( 'x2', 'x1', 'x3' ),
+				'alphabetic',
+				array( 'alphabetic' => array() ),
+				array(),
+				array( 'x1', 'x2', 'x3' )
+			),
+			array(
+				array( 'x2', 'x1', 'en', 'de', 'a2', 'a1' ),
+				'alphabetic',
+				$sortOrders,
+				array(),
+				array( 'de', 'en', 'a1', 'a2', 'x1', 'x2' )
+			),
+			array(
+				array( 'f', 'd', 'b', 'a', 'c', 'e' ),
+				'alphabetic',
+				array( 'alphabetic' => array( 'c', 'a' ) ),
+				array( 'e' ),
+				array( 'e', 'c', 'a', 'b', 'd', 'f' )
+			),
+			'Strict code order' => array(
+				array( 'f', 'd', 'b', 'a', 'c', 'e' ),
+				'code',
+				array( 'alphabetic' => array( 'c', 'a' ) ), // this should be ignored
+				array( 'e' ), // prepend
+				array( 'e', 'a', 'b', 'c', 'd', 'f' )
+			),
+			'Code w/o alphabetic' => array(
+				array( 'c', 'b', 'a' ),
+				'code',
+				array(),
+				array(),
+				array( 'a', 'b', 'c' )
+			),
+			array(
+				array( 'a', 'b', 'k', 'x' ),
+				'alphabetic',
+				array( 'alphabetic' => array( 'x', 'k', 'a' ) ),
+				array(),
+				array( 'x', 'k', 'a', 'b' )
+			),
+			'Fall back to code order' => array(
+				array( 'b', 'a' ),
+				'invalid',
+				array(),
+				array(),
+				array( 'a', 'b' )
+			)
+		);
+	}
+
+	/**
+	 * @dataProvider sortLinksProvider
+	 */
+	public function testSortLinks( array $links, $sort, array $sortOrders, $sortPrepend, $expected ) {
+		$interwikiSorter = new InterwikiSorter( $sort, $sortOrders, $sortPrepend );
+		$sortedLinks = $interwikiSorter->sortLinks( $links );
+		$this->assertEquals( $expected, $sortedLinks );
+	}
+
+}
diff --git a/tests/phpunit/InterwikiSortingHooksTest.php b/tests/phpunit/InterwikiSortingHooksTest.php
new file mode 100644
index 0000000..6bc79e1
--- /dev/null
+++ b/tests/phpunit/InterwikiSortingHooksTest.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace InterwikiSorting\Tests;
+
+use Hooks;
+use InterwikiSorting\InterwikiSortingHooks;
+use MediaWiki;
+use MediaWikiTestCase;
+
+/**
+ * @covers InterwikiSorting\InterwikiSortingHooks
+ *
+ * @license GPL-2.0+
+ * @author Addshore
+ */
+class InterwikiSortingHooksTest extends MediaWikiTestCase {
+
+	public function testHooksAreCorrectlyRegistered() {
+		$initHook = InterwikiSortingHooks::class . '::onBeforeInitialize';
+		$finalHook = [ InterwikiSortingHooks::class, 'onContentAlterParserOutput' ];
+
+		// Make sure the first hook has been registered
+		$this->assertContains( $initHook, Hooks::getHandlers( 'BeforeInitialize' ) );
+
+		// Fire the init hook which should register the second hook.
+		$initHook();
+
+		// Make sure that the hook has been registered and is at the end of the list.
+		$onContentAlterParserOutputHooks = Hooks::getHandlers( 'ContentAlterParserOutput' );
+		$this->assertContains( $finalHook, $onContentAlterParserOutputHooks );
+		$this->assertEquals(
+			$finalHook,
+			end( $onContentAlterParserOutputHooks ),
+			'Hook should be the last to be fired'
+		);
+
+	}
+
+}
\ No newline at end of file