diff --git a/.github/changelog/1552-from-description b/.github/changelog/1552-from-description
new file mode 100644
index 000000000..84eea39b2
--- /dev/null
+++ b/.github/changelog/1552-from-description
@@ -0,0 +1,4 @@
+Significance: patch
+Type: changed
+
+Add option to enable/disable the `Vary` Header to the "Advanced Settings".
diff --git a/activitypub.php b/activitypub.php
index ca3672e92..0a89fded8 100644
--- a/activitypub.php
+++ b/activitypub.php
@@ -67,16 +67,17 @@ function rest_init() {
  * Initialize plugin.
  */
 function plugin_init() {
-	\add_action( 'init', array( __NAMESPACE__ . '\Migration', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Activitypub', 'init' ) );
+	\add_action( 'init', array( __NAMESPACE__ . '\Comment', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Dispatcher', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Handler', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Hashtag', 'init' ) );
-	\add_action( 'init', array( __NAMESPACE__ . '\Mention', 'init' ) );
-	\add_action( 'init', array( __NAMESPACE__ . '\Scheduler', 'init' ) );
-	\add_action( 'init', array( __NAMESPACE__ . '\Comment', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Link', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Mailer', 'init' ) );
+	\add_action( 'init', array( __NAMESPACE__ . '\Mention', 'init' ) );
+	\add_action( 'init', array( __NAMESPACE__ . '\Migration', 'init' ), 1 );
+	\add_action( 'init', array( __NAMESPACE__ . '\Options', 'init' ) );
+	\add_action( 'init', array( __NAMESPACE__ . '\Scheduler', 'init' ) );
 
 	if ( site_supports_blocks() ) {
 		\add_action( 'init', array( __NAMESPACE__ . '\Blocks', 'init' ) );
diff --git a/includes/class-activitypub.php b/includes/class-activitypub.php
index c623d0bd7..902050f01 100644
--- a/includes/class-activitypub.php
+++ b/includes/class-activitypub.php
@@ -49,15 +49,9 @@ public static function init() {
 
 		\add_action( 'updated_postmeta', array( self::class, 'updated_postmeta' ), 10, 4 );
 		\add_action( 'added_post_meta', array( self::class, 'updated_postmeta' ), 10, 4 );
-		\add_filter( 'pre_option_activitypub_actor_mode', array( self::class, 'pre_option_activitypub_actor_mode' ) );
-		\add_filter( 'pre_option_activitypub_authorized_fetch', array( self::class, 'pre_option_activitypub_authorized_fetch' ) );
-		\add_filter( 'pre_option_activitypub_shared_inbox', array( self::class, 'pre_option_activitypub_shared_inbox' ) );
 
 		\add_action( 'init', array( self::class, 'register_user_meta' ), 11 );
 
-		\add_filter( 'pre_option_activitypub_allow_likes', array( self::class, 'maybe_disable_interactions' ) );
-		\add_filter( 'pre_option_activitypub_allow_replies', array( self::class, 'maybe_disable_interactions' ) );
-
 		// Register several post_types.
 		self::register_post_types();
 
@@ -96,37 +90,38 @@ public static function uninstall() {
 		\remove_filter( 'pre_wp_update_comment_count_now', array( Comment::class, 'pre_wp_update_comment_count_now' ) );
 		Migration::update_comment_counts( 2000 );
 
-		delete_option( 'activitypub_actor_mode' );
-		delete_option( 'activitypub_allow_likes' );
-		delete_option( 'activitypub_allow_replies' );
-		delete_option( 'activitypub_attribution_domains' );
-		delete_option( 'activitypub_authorized_fetch' );
-		delete_option( 'activitypub_application_user_private_key' );
-		delete_option( 'activitypub_application_user_public_key' );
-		delete_option( 'activitypub_blog_user_also_known_as' );
-		delete_option( 'activitypub_blog_user_moved_to' );
-		delete_option( 'activitypub_blog_user_private_key' );
-		delete_option( 'activitypub_blog_user_public_key' );
-		delete_option( 'activitypub_blog_description' );
-		delete_option( 'activitypub_blog_identifier' );
-		delete_option( 'activitypub_custom_post_content' );
-		delete_option( 'activitypub_db_version' );
-		delete_option( 'activitypub_default_extra_fields' );
-		delete_option( 'activitypub_enable_blog_user' );
-		delete_option( 'activitypub_enable_users' );
-		delete_option( 'activitypub_header_image' );
-		delete_option( 'activitypub_last_post_with_permalink_as_id' );
-		delete_option( 'activitypub_mailer_new_follower' );
-		delete_option( 'activitypub_mailer_new_dm' );
-		delete_option( 'activitypub_max_image_attachments' );
-		delete_option( 'activitypub_migration_lock' );
-		delete_option( 'activitypub_object_type' );
-		delete_option( 'activitypub_outbox_purge_days' );
-		delete_option( 'activitypub_shared_inbox' );
-		delete_option( 'activitypub_support_post_types' );
-		delete_option( 'activitypub_use_hashtags' );
-		delete_option( 'activitypub_use_opengraph' );
-		delete_option( 'activitypub_use_permalink_as_id_for_blog' );
+		\delete_option( 'activitypub_actor_mode' );
+		\delete_option( 'activitypub_allow_likes' );
+		\delete_option( 'activitypub_allow_replies' );
+		\delete_option( 'activitypub_attribution_domains' );
+		\delete_option( 'activitypub_authorized_fetch' );
+		\delete_option( 'activitypub_application_user_private_key' );
+		\delete_option( 'activitypub_application_user_public_key' );
+		\delete_option( 'activitypub_blog_user_also_known_as' );
+		\delete_option( 'activitypub_blog_user_moved_to' );
+		\delete_option( 'activitypub_blog_user_private_key' );
+		\delete_option( 'activitypub_blog_user_public_key' );
+		\delete_option( 'activitypub_blog_description' );
+		\delete_option( 'activitypub_blog_identifier' );
+		\delete_option( 'activitypub_custom_post_content' );
+		\delete_option( 'activitypub_db_version' );
+		\delete_option( 'activitypub_default_extra_fields' );
+		\delete_option( 'activitypub_enable_blog_user' );
+		\delete_option( 'activitypub_enable_users' );
+		\delete_option( 'activitypub_header_image' );
+		\delete_option( 'activitypub_last_post_with_permalink_as_id' );
+		\delete_option( 'activitypub_mailer_new_follower' );
+		\delete_option( 'activitypub_mailer_new_dm' );
+		\delete_option( 'activitypub_max_image_attachments' );
+		\delete_option( 'activitypub_migration_lock' );
+		\delete_option( 'activitypub_object_type' );
+		\delete_option( 'activitypub_outbox_purge_days' );
+		\delete_option( 'activitypub_shared_inbox' );
+		\delete_option( 'activitypub_support_post_types' );
+		\delete_option( 'activitypub_use_hashtags' );
+		\delete_option( 'activitypub_use_opengraph' );
+		\delete_option( 'activitypub_use_permalink_as_id_for_blog' );
+		\delete_option( 'activitypub_vary_header' );
 	}
 
 	/**
@@ -209,7 +204,7 @@ public static function add_headers() {
 		if ( ! headers_sent() ) {
 			\header( 'Link: <' . esc_url( $id ) . '>; title="ActivityPub (JSON)"; rel="alternate"; type="application/activity+json"', false );
 
-			if ( ACTIVITYPUB_SEND_VARY_HEADER ) {
+			if ( \get_option( 'activitypub_vary_header' ) ) {
 				// Send Vary header for Accept header.
 				\header( 'Vary: Accept', false );
 			}
@@ -396,68 +391,6 @@ public static function pre_get_avatar_data( $args, $id_or_email ) {
 		return $args;
 	}
 
-	/**
-	 * Pre-get option filter for the Actor-Mode.
-	 *
-	 * @param string|false $pre The pre-get option value.
-	 *
-	 * @return string|false The actor mode or false if it should not be filtered.
-	 */
-	public static function pre_option_activitypub_actor_mode( $pre ) {
-		if ( \defined( 'ACTIVITYPUB_SINGLE_USER_MODE' ) && ACTIVITYPUB_SINGLE_USER_MODE ) {
-			return ACTIVITYPUB_BLOG_MODE;
-		}
-
-		if ( \defined( 'ACTIVITYPUB_DISABLE_USER' ) && ACTIVITYPUB_DISABLE_USER ) {
-			return ACTIVITYPUB_BLOG_MODE;
-		}
-
-		if ( \defined( 'ACTIVITYPUB_DISABLE_BLOG_USER' ) && ACTIVITYPUB_DISABLE_BLOG_USER ) {
-			return ACTIVITYPUB_ACTOR_MODE;
-		}
-
-		return $pre;
-	}
-
-	/**
-	 * Pre-get option filter for the Authorized Fetch.
-	 *
-	 * @param string $pre The pre-get option value.
-	 *
-	 * @return string If the constant is defined, return the value, otherwise return the pre-get option value.
-	 */
-	public static function pre_option_activitypub_authorized_fetch( $pre ) {
-		if ( ! \defined( 'ACTIVITYPUB_AUTHORIZED_FETCH' ) ) {
-			return $pre;
-		}
-
-		if ( ACTIVITYPUB_AUTHORIZED_FETCH ) {
-			return '1';
-		}
-
-		return '0';
-	}
-
-	/**
-	 * Pre-get option filter for the Shared Inbox.
-	 *
-	 * @param string $pre The pre-get option value.
-	 *
-	 * @return string If the constant is defined, return the value, otherwise return the pre-get option value.
-	 */
-	public static function pre_option_activitypub_shared_inbox( $pre ) {
-		if ( ! \defined( 'ACTIVITYPUB_SHARED_INBOX_FEATURE' ) ) {
-			return $pre;
-		}
-
-		if ( ACTIVITYPUB_SHARED_INBOX_FEATURE ) {
-			return '1';
-		}
-
-		return '0';
-	}
-
-
 	/**
 	 * Store permalink in meta, to send delete Activity.
 	 *
@@ -902,18 +835,4 @@ public static function register_user_meta() {
 			)
 		);
 	}
-
-	/**
-	 * Disallow interactions if the constant is set.
-	 *
-	 * @param bool $pre_option The value of the option.
-	 * @return bool|string The value of the option.
-	 */
-	public static function maybe_disable_interactions( $pre_option ) {
-		if ( ACTIVITYPUB_DISABLE_INCOMING_INTERACTIONS ) {
-			return '0';
-		}
-
-		return $pre_option;
-	}
 }
diff --git a/includes/class-options.php b/includes/class-options.php
new file mode 100644
index 000000000..d30ef9ade
--- /dev/null
+++ b/includes/class-options.php
@@ -0,0 +1,124 @@
+<?php
+/**
+ * Options file.
+ *
+ * @package ActivityPub
+ */
+
+namespace ActivityPub;
+
+/**
+ * Options class.
+ *
+ * @package ActivityPub
+ */
+class Options {
+
+	/**
+	 * Initialize the options.
+	 */
+	public static function init() {
+		\add_filter( 'pre_option_activitypub_actor_mode', array( self::class, 'pre_option_activitypub_actor_mode' ) );
+		\add_filter( 'pre_option_activitypub_authorized_fetch', array( self::class, 'pre_option_activitypub_authorized_fetch' ) );
+		\add_filter( 'pre_option_activitypub_shared_inbox', array( self::class, 'pre_option_activitypub_shared_inbox' ) );
+		\add_filter( 'pre_option_activitypub_vary_header', array( self::class, 'pre_option_activitypub_vary_header' ) );
+
+		\add_filter( 'pre_option_activitypub_allow_likes', array( self::class, 'maybe_disable_interactions' ) );
+		\add_filter( 'pre_option_activitypub_allow_replies', array( self::class, 'maybe_disable_interactions' ) );
+	}
+
+
+	/**
+	 * Pre-get option filter for the Actor-Mode.
+	 *
+	 * @param string|false $pre The pre-get option value.
+	 *
+	 * @return string|false The actor mode or false if it should not be filtered.
+	 */
+	public static function pre_option_activitypub_actor_mode( $pre ) {
+		if ( \defined( 'ACTIVITYPUB_SINGLE_USER_MODE' ) && ACTIVITYPUB_SINGLE_USER_MODE ) {
+			return ACTIVITYPUB_BLOG_MODE;
+		}
+
+		if ( \defined( 'ACTIVITYPUB_DISABLE_USER' ) && ACTIVITYPUB_DISABLE_USER ) {
+			return ACTIVITYPUB_BLOG_MODE;
+		}
+
+		if ( \defined( 'ACTIVITYPUB_DISABLE_BLOG_USER' ) && ACTIVITYPUB_DISABLE_BLOG_USER ) {
+			return ACTIVITYPUB_ACTOR_MODE;
+		}
+
+		return $pre;
+	}
+
+	/**
+	 * Pre-get option filter for the Authorized Fetch.
+	 *
+	 * @param string $pre The pre-get option value.
+	 *
+	 * @return string If the constant is defined, return the value, otherwise return the pre-get option value.
+	 */
+	public static function pre_option_activitypub_authorized_fetch( $pre ) {
+		if ( ! \defined( 'ACTIVITYPUB_AUTHORIZED_FETCH' ) ) {
+			return $pre;
+		}
+
+		if ( ACTIVITYPUB_AUTHORIZED_FETCH ) {
+			return '1';
+		}
+
+		return '0';
+	}
+
+	/**
+	 * Pre-get option filter for the Shared Inbox.
+	 *
+	 * @param string $pre The pre-get option value.
+	 *
+	 * @return string If the constant is defined, return the value, otherwise return the pre-get option value.
+	 */
+	public static function pre_option_activitypub_shared_inbox( $pre ) {
+		if ( ! \defined( 'ACTIVITYPUB_SHARED_INBOX_FEATURE' ) ) {
+			return $pre;
+		}
+
+		if ( ACTIVITYPUB_SHARED_INBOX_FEATURE ) {
+			return '1';
+		}
+
+		return '0';
+	}
+
+	/**
+	 * Pre-get option filter for the Vary Header.
+	 *
+	 * @param string $pre The pre-get option value.
+	 *
+	 * @return string If the constant is defined, return the value, otherwise return the pre-get option value.
+	 */
+	public static function pre_option_activitypub_vary_header( $pre ) {
+		if ( ! \defined( 'ACTIVITYPUB_SEND_VARY_HEADER' ) ) {
+			return $pre;
+		}
+
+		if ( ACTIVITYPUB_SEND_VARY_HEADER ) {
+			return '1';
+		}
+
+		return '0';
+	}
+
+	/**
+	 * Disallow interactions if the constant is set.
+	 *
+	 * @param bool $pre_option The value of the option.
+	 * @return bool|string The value of the option.
+	 */
+	public static function maybe_disable_interactions( $pre_option ) {
+		if ( ACTIVITYPUB_DISABLE_INCOMING_INTERACTIONS ) {
+			return '0';
+		}
+
+		return $pre_option;
+	}
+}
diff --git a/includes/constants.php b/includes/constants.php
index 6adfce393..8b6c92d07 100644
--- a/includes/constants.php
+++ b/includes/constants.php
@@ -19,7 +19,6 @@
 \defined( 'ACTIVITYPUB_DISABLE_REWRITES' ) || \define( 'ACTIVITYPUB_DISABLE_REWRITES', false );
 \defined( 'ACTIVITYPUB_DISABLE_INCOMING_INTERACTIONS' ) || \define( 'ACTIVITYPUB_DISABLE_INCOMING_INTERACTIONS', false );
 \defined( 'ACTIVITYPUB_DISABLE_OUTGOING_INTERACTIONS' ) || \define( 'ACTIVITYPUB_DISABLE_OUTGOING_INTERACTIONS', false );
-\defined( 'ACTIVITYPUB_SEND_VARY_HEADER' ) || \define( 'ACTIVITYPUB_SEND_VARY_HEADER', false );
 \defined( 'ACTIVITYPUB_DEFAULT_OBJECT_TYPE' ) || \define( 'ACTIVITYPUB_DEFAULT_OBJECT_TYPE', 'wordpress-post-format' );
 \defined( 'ACTIVITYPUB_OUTBOX_PROCESSING_BATCH_SIZE' ) || \define( 'ACTIVITYPUB_OUTBOX_PROCESSING_BATCH_SIZE', 100 );
 
diff --git a/includes/wp-admin/class-advanced-settings-fields.php b/includes/wp-admin/class-advanced-settings-fields.php
index 81c521822..056f02df8 100644
--- a/includes/wp-admin/class-advanced-settings-fields.php
+++ b/includes/wp-admin/class-advanced-settings-fields.php
@@ -39,6 +39,17 @@ public static function register_advanced_fields() {
 			array( 'label_for' => 'activitypub_outbox_purge_days' )
 		);
 
+		if ( ! defined( 'ACTIVITYPUB_SEND_VARY_HEADER' ) ) {
+			\add_settings_field(
+				'activitypub_vary_header',
+				\__( 'Vary Header', 'activitypub' ),
+				array( self::class, 'render_vary_header_field' ),
+				'activitypub_advanced_settings',
+				'activitypub_advanced_settings',
+				array( 'label_for' => 'activitypub_vary_header' )
+			);
+		}
+
 		if ( ! defined( 'ACTIVITYPUB_AUTHORIZED_FETCH' ) ) {
 			\add_settings_field(
 				'activitypub_authorized_fetch',
@@ -101,6 +112,24 @@ public static function render_outbox_purge_days_field() {
 		) . '</p>';
 	}
 
+	/**
+	 * Render vary header field.
+	 */
+	public static function render_vary_header_field() {
+		$value = \get_option( 'activitypub_vary_header', '0' );
+		?>
+		<p>
+			<label>
+				<input type="checkbox" id="activitypub_vary_header" name="activitypub_vary_header" value="1" <?php checked( '1', $value ); ?> />
+				<?php echo \wp_kses( \__( 'Help prevent incorrect caching of ActivityPub responses.', 'activitypub' ), array( 'code' => array() ) ); ?>
+			</label>
+		</p>
+		<p class="description">
+			<?php \esc_html_e( 'Enable this if you notice your site showing technical content instead of normal web pages, or if your ActivityPub connections seem unreliable. This setting helps your site deliver the right format of content to different services automatically.', 'activitypub' ); ?>
+		</p>
+		<?php
+	}
+
 	/**
 	 * Render use Authorized Fetch field.
 	 */
diff --git a/includes/wp-admin/class-health-check.php b/includes/wp-admin/class-health-check.php
index 3c4d5ae99..343cc1f48 100644
--- a/includes/wp-admin/class-health-check.php
+++ b/includes/wp-admin/class-health-check.php
@@ -326,6 +326,12 @@ public static function debug_information( $info ) {
 			'private' => false,
 		);
 
+		$info['activitypub']['fields']['vary_header'] = array(
+			'label'   => \__( 'Vary Header', 'activitypub' ),
+			'value'   => \esc_attr( (int) \get_option( 'activitypub_vary_header', '0' ) ),
+			'private' => false,
+		);
+
 		$info['activitypub']['fields']['shared_inbox'] = array(
 			'label'   => \__( 'Shared Inbox', 'activitypub' ),
 			'value'   => \esc_attr( (int) \get_option( 'activitypub_shared_inbox', '0' ) ),
diff --git a/includes/wp-admin/class-settings.php b/includes/wp-admin/class-settings.php
index 537a56c46..c0d9f4d0f 100644
--- a/includes/wp-admin/class-settings.php
+++ b/includes/wp-admin/class-settings.php
@@ -177,6 +177,16 @@ public static function register_settings() {
 			)
 		);
 
+		\register_setting(
+			'activitypub_advanced',
+			'activitypub_vary_header',
+			array(
+				'type'        => 'boolean',
+				'description' => \__( 'Add the Vary header to the ActivityPub response.', 'activitypub' ),
+				'default'     => false,
+			)
+		);
+
 		\register_setting(
 			'activitypub_advanced',
 			'activitypub_authorized_fetch',