diff --git a/includes/Constants.php b/includes/Constants.php
index b8a37a6..c4cafb9 100644
--- a/includes/Constants.php
+++ b/includes/Constants.php
@@ -79,6 +79,11 @@ final class Constants {
 	 */
 	public const CONFIG_SEARCH_IN_HEADER = 'VectorIsSearchInHeader';
 
+	/**
+	 * @var string
+	 */
+	public const CONFIG_SEARCH_IN_HEADER_AB = 'VectorIsSearchInHeaderABTest';
+
 	/**
 	 * @var string
 	 */
diff --git a/includes/FeatureManagement/Requirements/SearchInHeaderRequirement.php b/includes/FeatureManagement/Requirements/SearchInHeaderRequirement.php
index 71cfb7c..fa2260c 100644
--- a/includes/FeatureManagement/Requirements/SearchInHeaderRequirement.php
+++ b/includes/FeatureManagement/Requirements/SearchInHeaderRequirement.php
@@ -31,6 +31,9 @@ use Vector\FeatureManagement\Requirement;
  * the tabs (as in the old design).
  * The search in header is enabled if:
  *  - the associated feature flag has been enabled
+ *  - the feature flag for the A/B test is enabled,
+ *     and the user is logged and bucketed,
+ *     in which case 50% of logged in users will see the search in the header
  *
  * @unstable
  *
@@ -43,14 +46,21 @@ final class SearchInHeaderRequirement implements Requirement {
 	 */
 	private $config;
 
+	/**
+	 * @var \User
+	 */
+	private $user;
+
 	/**
 	 * This constructor accepts all dependencies needed to determine
 	 * whether search in header is enabled for current user and config.
 	 *
 	 * @param \Config $config
+	 * @param \User $user
 	 */
-	public function __construct( Config $config ) {
+	public function __construct( \Config $config, \User $user ) {
 		$this->config = $config;
+		$this->user = $user;
 	}
 
 	/**
@@ -60,11 +70,27 @@ final class SearchInHeaderRequirement implements Requirement {
 		return Constants::REQUIREMENT_SEARCH_IN_HEADER;
 	}
 
+	/**
+	 * If A/B test is enabled check whether the user is logged in and bucketed
+	 * @return bool
+	 */
+	private function isBucketed() {
+		$isABTestEnabled = (bool)$this->config->get( Constants::CONFIG_SEARCH_IN_HEADER_AB );
+
+		if ( $isABTestEnabled ) {
+			return $this->user->getId() % 2 === 0;
+		} else {
+			// if A/B test is disabled then resort to using CONFIG_SEARCH_IN_HEADER
+			return (bool)$this->config->get( Constants::CONFIG_SEARCH_IN_HEADER );
+		}
+	}
+
 	/**
 	 * @inheritDoc
 	 * @throws \ConfigException
 	 */
 	public function isMet() : bool {
-		return (bool)$this->config->get( Constants::CONFIG_SEARCH_IN_HEADER );
+		return $this->user->isRegistered() ?
+			$this->isBucketed() : (bool)$this->config->get( Constants::CONFIG_SEARCH_IN_HEADER );
 	}
 }
diff --git a/includes/ServiceWiring.php b/includes/ServiceWiring.php
index 3fcc0ad..2c63182 100644
--- a/includes/ServiceWiring.php
+++ b/includes/ServiceWiring.php
@@ -71,7 +71,8 @@ return [
 		// ========================================
 		$featureManager->registerRequirement(
 			new SearchInHeaderRequirement(
-				$services->getMainConfig()
+				$services->getMainConfig(),
+				$context->getUser()
 			)
 		);
 
diff --git a/skin.json b/skin.json
index 7e32ca6..70db03a 100644
--- a/skin.json
+++ b/skin.json
@@ -189,6 +189,9 @@
 		"VectorIsSearchInHeader": {
 			"value": false
 		},
+		"VectorIsSearchInHeaderABTest": {
+			"value": false
+		},
 		"VectorDefaultSidebarVisibleForAuthorisedUser": {
 			"value": true
 		},
diff --git a/tests/phpunit/integration/FeatureManagement/Requirements/SearchInHeaderRequirementTest.php b/tests/phpunit/integration/FeatureManagement/Requirements/SearchInHeaderRequirementTest.php
new file mode 100644
index 0000000..a4f5576
--- /dev/null
+++ b/tests/phpunit/integration/FeatureManagement/Requirements/SearchInHeaderRequirementTest.php
@@ -0,0 +1,127 @@
+<?php
+/**
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @since 1.36
+ */
+
+use Vector\Constants;
+use Vector\FeatureManagement\Requirements\SearchInHeaderRequirement;
+
+/**
+ * @group Vector
+ * @coversDefaultClass \Vector\FeatureManagement\Requirements\SearchInHeaderRequirement
+ */
+class SearchInHeaderRequirementTest extends \MediaWikiTestCase {
+
+	public function providerSearchInHeaderRequirement() {
+		return [
+			[
+				// Is enabled for anons
+				false,
+				// is A-B test enabled
+				false,
+				// note 0 = anon user
+				0,
+				false,
+				'If nothing enabled nobody gets search in header'
+			],
+			[
+				// Is enabled for anons
+				true,
+				// is A-B test enabled
+				false,
+				// note 0 = anon user
+				0,
+				true,
+				'All anons should get search in header if enable but when A/B test disabled'
+			],
+			[
+				// Is enabled for anons
+				true,
+				// is A-B test enabled
+				false,
+				0,
+				true,
+				'All even logged in users should get search in header when A/B test disabled'
+			],
+			[
+				// Is enabled for anons
+				true,
+				// is A-B test enabled
+				false,
+				1,
+				true,
+				'All odd logged in users should get search in header when A/B test disabled'
+			],
+			[
+				// Is enabled for anons
+				true,
+				// is A-B test enabled
+				true,
+				// note 0 = anon user
+				0,
+				true,
+				'All anons get search in header even when A/B enabled'
+			],
+			[
+				// Is enabled for anons
+				true,
+				// is A-B test enabled
+				true,
+				2,
+				true,
+				'Bucketed users get search in header when A/B test enabled'
+			],
+			[
+				// Is enabled for anons
+				true,
+				// is A-B test enabled
+				true,
+				1,
+				false,
+				'Non-Bucketed users do not get search in header when A/B test enabled'
+			],
+		];
+	}
+
+	/**
+	 * @covers ::isMet
+	 * @dataProvider providerSearchInHeaderRequirement
+	 * @param bool $searchInHeaderConfigValue
+	 * @param bool $abValue
+	 * @param int $userId
+	 * @param bool $expected
+	 * @param string $msg
+	 */
+	public function testSearchInHeaderRequirement(
+		$searchInHeaderConfigValue, $abValue, $userId, $expected, $msg
+	) {
+		$config = new HashConfig( [
+			Constants::CONFIG_SEARCH_IN_HEADER => $searchInHeaderConfigValue,
+			Constants::CONFIG_SEARCH_IN_HEADER_AB => $abValue,
+		] );
+		$user = $this->getTestUser()->getUser();
+		$user->setId( $userId );
+
+		$requirement = new SearchInHeaderRequirement(
+			$config, $user
+		);
+
+		$this->assertSame( $requirement->isMet(), $expected, $msg );
+	}
+}