diff --git a/google_tag.info.yml b/google_tag.info.yml
index 15f70e2..6ce8710 100644
--- a/google_tag.info.yml
+++ b/google_tag.info.yml
@@ -2,5 +2,5 @@ name: 'Google Tag Manager'
 type: module
 description: 'Allows your website analytics to be managed using Google Tag Manager.'
 package: 'Statistics'
-core: 8.x
+core_version_requirement: ^8 || ^9
 configure: google_tag.settings_form
diff --git a/google_tag.install b/google_tag.install
index 035d4a4..3020a70 100644
--- a/google_tag.install
+++ b/google_tag.install
@@ -8,6 +8,8 @@
  */
 
 use Drupal\Core\StreamWrapper\PublicStream;
+use Drupal\Core\File\FileSystemInterface;
+use Drupal\Core\Url;
 
 /**
  * Implements hook_requirements().
@@ -20,7 +22,7 @@ function google_tag_requirements($phase) {
       // Google Tag Manager container ID has not been set.
       $requirements['google_tag'] = array(
         'title' => t('Google Tag Manager'),
-        'description' => t('Configure this integration module on its <a href=":url">settings page</a>.', array(':url' => \Drupal::url('google_tag.settings_form'))),
+        'description' => t('Configure this integration module on its <a href=":url">settings page</a>.', array(':url' => Url::fromRoute('google_tag.settings_form')->toString())),
         'severity' => REQUIREMENT_WARNING,
         'value' => t('Not configured'),
       );
@@ -29,8 +31,10 @@ function google_tag_requirements($phase) {
   if ($phase == 'runtime' || $phase == 'install') {
     // Adapted from system_requirements().
     $directory = PublicStream::basePath() . '/js';
+    /** @var \Drupal\Core\File\FileSystemInterface $fileSystem */
+    $fileSystem = \Drupal::service('file_system');
     if (!is_dir($directory) || !is_writable($directory)) {
-      file_prepare_directory($directory, FILE_CREATE_DIRECTORY | FILE_MODIFY_PERMISSIONS);
+      $fileSystem->prepareDirectory($directory, FileSystemInterface::CREATE_DIRECTORY | FileSystemInterface::MODIFY_PERMISSIONS);
     }
     $is_writable = is_writable($directory);
     $is_directory = is_dir($directory);
diff --git a/google_tag.module b/google_tag.module
index 19d7a50..bec1c24 100644
--- a/google_tag.module
+++ b/google_tag.module
@@ -12,6 +12,8 @@
 
 use Drupal\Component\Utility\Unicode;
 use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\File\FileSystemInterface;
+use Drupal\Core\Messenger\MessengerInterface;
 
 /**
  * Default for matching all items except listed.
@@ -293,9 +295,11 @@ function google_tag_save_snippets() {
   $saved = FALSE; $unsaved = FALSE;
   $dir = _google_tag_get_js_dir();
   $snippets = google_tag_snippets();
+  /** @var \Drupal\Core\File\FileSystemInterface $fileSystem */
+  $fileSystem = \Drupal::service('file_system');
   foreach ($snippets as $type => $snippet) {
-    if ($dir_exists = file_prepare_directory($dir, FILE_CREATE_DIRECTORY)) {
-      $path = file_unmanaged_save_data($snippet, "{$dir}/google_tag.{$type}.js", FILE_EXISTS_REPLACE);
+    if ($dir_exists = $fileSystem->prepareDirectory($dir, FileSystemInterface::CREATE_DIRECTORY)) {
+      $path = $fileSystem->saveData($snippet, "{$dir}/google_tag.{$type}.js", FileSystemInterface::EXISTS_REPLACE);
     }
     if ($dir_exists === TRUE && $path !== FALSE) {
       $saved = TRUE;
@@ -306,7 +310,10 @@ function google_tag_save_snippets() {
 
   }
   if ($unsaved) {
-    drupal_set_message(t('An error occurred saving one or more snippet files. Please try again or contact the site administrator if it persists.'));
+    \Drupal::messenger()->addMessage(
+      t('An error occurred saving one or more snippet files. Please try again or contact the site administrator if it persists.'),
+      MessengerInterface::TYPE_STATUS
+    );
   }
   if ($saved) {
     \Drupal::service('asset.js.collection_optimizer')->deleteAll();