diff -u b/core/modules/user/src/Controller/UserAuthenticationController.php b/core/modules/user/src/Controller/UserAuthenticationController.php
--- b/core/modules/user/src/Controller/UserAuthenticationController.php
+++ b/core/modules/user/src/Controller/UserAuthenticationController.php
@@ -309,7 +309,7 @@
     $format = $request->getRequestFormat();
     $this->userLogout();
     $response_data['msg'] = 'Logged out successfully.';
-    return new Response($this->serializer->encode($response_data, $format), 204);
+    return new Response($this->serializer->encode($response_data, $format));
   }
 
   /**
only in patch2:
unchanged:
--- a/core/modules/user/tests/src/Functional/UserLoginHttpTest.php
+++ b/core/modules/user/tests/src/Functional/UserLoginHttpTest.php
@@ -197,7 +197,7 @@ protected function doTestLogin($format) {
     $this->assertHttpResponse($response, 200, UserAuthenticationController::LOGGED_IN);
 
     $response = $this->logoutRequest($format, $logout_token);
-    $this->assertEquals(204, $response->getStatusCode());
+    $this->assertEquals(200, $response->getStatusCode());
 
     $response = $client->get($login_status_url, ['cookies' => $this->cookies]);
     $this->assertHttpResponse($response, 200, UserAuthenticationController::LOGGED_OUT);
@@ -487,7 +487,7 @@ public function testLogoutCsrfProtection() {
 
     // Try a logout request with correct token.
     $response = $this->logoutRequest('json', $logout_token);
-    $this->assertEquals(204, $response->getStatusCode());
+    $this->assertEquals(200, $response->getStatusCode());
 
     // Ensure actually logged out.
     $response = $client->get($login_status_url, ['cookies' => $this->cookies]);