diff --git a/bootstrap.php b/bootstrap.php
index a978f18..c90355b 100644
--- a/bootstrap.php
+++ b/bootstrap.php
@@ -43,6 +43,7 @@
 define( 'GTM_SERVER_SIDE_ADMIN_GROUP_GENERAL', 'gtm-server-side-admin-group-general' );
 define( 'GTM_SERVER_SIDE_ADMIN_GROUP_DATA_LAYER', 'gtm-server-side-admin-group-data-layer' );
 define( 'GTM_SERVER_SIDE_ADMIN_GROUP_WEBHOOKS', 'gtm-server-side-admin-group-webhooks' );
+define( 'GTM_SENSITIVE_DATA_NOTICE', '<!-- DO NOT CACHE -->' );
 
 // Autoload plugin classes.
 spl_autoload_register(
diff --git a/includes/class-gtm-server-side-admin-settings.php b/includes/class-gtm-server-side-admin-settings.php
index 42af988..bf1752f 100644
--- a/includes/class-gtm-server-side-admin-settings.php
+++ b/includes/class-gtm-server-side-admin-settings.php
@@ -271,7 +271,7 @@ function() {
 					' . checked( GTM_Server_Side_Helpers::get_option( GTM_SERVER_SIDE_FIELD_DATA_LAYER_ECOMMERCE ), 'yes', false ) . '
 					value="yes">';
 				echo '<br>';
-				esc_html_e( 'This option only works with Woocommerce shops. Adds basic events and their data: Login, SignUp, ViewItem, AddToCart, BeginCheckout, Purchase.', 'gtm-server-side' );
+				esc_html_e( 'This option only works with Woocommerce shops. Adds basic events and their data: Login, SignUp, ViewItem, AddToCart, BeginCheckout, Purchase. On cached websites ensure to implement gtm_server_side_is_page_cached filter.', 'gtm-server-side' );
 			},
 			GTM_SERVER_SIDE_ADMIN_SLUG,
 			GTM_SERVER_SIDE_ADMIN_GROUP_DATA_LAYER
@@ -295,7 +295,7 @@ function() {
 					' . checked( GTM_Server_Side_Helpers::get_option( GTM_SERVER_SIDE_FIELD_DATA_LAYER_USER_DATA ), 'yes', false ) . '
 					value="yes">';
 				echo '<br>';
-				esc_html_e( 'All events for authorised users will have their personal details (name, surname, email, etc.) available. Their billing details will be available on the purchase event.', 'gtm-server-side' );
+				esc_html_e( 'All events for authorised users on uncached pages, will have their personal details (name, surname, email, etc.) available. Their billing details will be available on the purchase event. Page is marked as cached using `gtm_server_side_is_page_cached` filter.', 'gtm-server-side' );
 			},
 			GTM_SERVER_SIDE_ADMIN_SLUG,
 			GTM_SERVER_SIDE_ADMIN_GROUP_DATA_LAYER
diff --git a/includes/class-gtm-server-side-event-begincheckout.php b/includes/class-gtm-server-side-event-begincheckout.php
index d591c30..42efe40 100644
--- a/includes/class-gtm-server-side-event-begincheckout.php
+++ b/includes/class-gtm-server-side-event-begincheckout.php
@@ -34,6 +34,10 @@ public function init() {
 	 * @return void
 	 */
 	public function wp_footer() {
+		if ( ! GTM_Server_Side_Helpers::can_output_sensitive_data() ) {
+			return;
+		}
+
 		if ( ! is_checkout() ) {
 			return;
 		}
@@ -55,9 +59,10 @@ public function wp_footer() {
 			),
 		);
 
-		if ( GTM_Server_Side_WC_Helpers::instance()->is_enable_user_data() ) {
+		if ( GTM_Server_Side_WC_Helpers::instance()->should_output_user_data() ) {
 			$data_layer['user_data'] = GTM_Server_Side_WC_Helpers::instance()->get_data_layer_user_data();
 		}
+		echo GTM_SENSITIVE_DATA_NOTICE; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 		?>
 		<script type="text/javascript">
 			dataLayer.push( { ecommerce: null } );
diff --git a/includes/class-gtm-server-side-event-login.php b/includes/class-gtm-server-side-event-login.php
index 3ff2483..4e7da70 100644
--- a/includes/class-gtm-server-side-event-login.php
+++ b/includes/class-gtm-server-side-event-login.php
@@ -52,6 +52,10 @@ public function wp_login() {
 	 * @return void
 	 */
 	public function wp_footer() {
+		if ( ! GTM_Server_Side_Helpers::can_output_sensitive_data() ) {
+			return;
+		}
+
 		if ( ! GTM_Server_Side_Helpers::exists_session( self::CHECK_NAME, GTM_SERVER_SIDE_FIELD_VALUE_YES ) ) {
 			return;
 		}
@@ -60,10 +64,11 @@ public function wp_footer() {
 			'event' => GTM_Server_Side_Helpers::get_data_layer_event_name( 'login' ),
 		);
 
-		if ( GTM_Server_Side_WC_Helpers::instance()->is_enable_user_data() ) {
+		if ( GTM_Server_Side_WC_Helpers::instance()->should_output_user_data() ) {
 			$data_layer['user_data'] = GTM_Server_Side_WC_Helpers::instance()->get_data_layer_user_data();
 		}
-		?>
+		echo GTM_SENSITIVE_DATA_NOTICE; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
+        ?>
 		<script type="text/javascript">
 			dataLayer.push( { ecommerce: null } );
 			dataLayer.push(<?php echo GTM_Server_Side_Helpers::array_to_json( $data_layer ); // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped ?>);
diff --git a/includes/class-gtm-server-side-event-purchase.php b/includes/class-gtm-server-side-event-purchase.php
index 8aef6b7..1817aa7 100644
--- a/includes/class-gtm-server-side-event-purchase.php
+++ b/includes/class-gtm-server-side-event-purchase.php
@@ -65,6 +65,10 @@ public function woocommerce_new_order( $order_id ) {
 	 * @return void
 	 */
 	public function wp_footer() {
+		if ( ! GTM_Server_Side_Helpers::can_output_sensitive_data() ) {
+			return;
+		}
+
 		/* phpcs:ignore
 		if ( ! is_wc_endpoint_url( 'order-received' ) ) {
 			return;
@@ -97,10 +101,11 @@ public function wp_footer() {
 			),
 		);
 
-		if ( GTM_Server_Side_WC_Helpers::instance()->is_enable_user_data() ) {
+		if ( GTM_Server_Side_WC_Helpers::instance()->should_output_user_data() ) {
 			$data_layer['user_data']                 = GTM_Server_Side_WC_Helpers::instance()->get_order_user_data( $order );
 			$data_layer['user_data']['new_customer'] = GTM_Server_Side_WC_Helpers::instance()->is_new_customer( $order->get_customer_id() ) ? 'true' : 'false';
 		}
+		echo GTM_SENSITIVE_DATA_NOTICE; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 		?>
 		<script type="text/javascript">
 			dataLayer.push( { ecommerce: null } );
diff --git a/includes/class-gtm-server-side-event-register.php b/includes/class-gtm-server-side-event-register.php
index 2539a64..d97f20a 100644
--- a/includes/class-gtm-server-side-event-register.php
+++ b/includes/class-gtm-server-side-event-register.php
@@ -52,6 +52,10 @@ public function user_register() {
 	 * @return void
 	 */
 	public function wp_footer() {
+		if ( ! GTM_Server_Side_Helpers::can_output_sensitive_data() ) {
+			return;
+		}
+
 		if ( ! GTM_Server_Side_Helpers::exists_session( self::CHECK_NAME, GTM_SERVER_SIDE_FIELD_VALUE_YES ) ) {
 			return;
 		}
@@ -60,9 +64,10 @@ public function wp_footer() {
 			'event' => GTM_Server_Side_Helpers::get_data_layer_event_name( 'sign_up' ),
 		);
 
-		if ( GTM_Server_Side_WC_Helpers::instance()->is_enable_user_data() ) {
+		if ( GTM_Server_Side_WC_Helpers::instance()->should_output_user_data() ) {
 			$data_layer['user_data'] = GTM_Server_Side_WC_Helpers::instance()->get_data_layer_user_data();
 		}
+		echo GTM_SENSITIVE_DATA_NOTICE; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 		?>
 		<script type="text/javascript">
 			dataLayer.push( { ecommerce: null } );
diff --git a/includes/class-gtm-server-side-event-viewcart.php b/includes/class-gtm-server-side-event-viewcart.php
index 0ac513b..280dddc 100644
--- a/includes/class-gtm-server-side-event-viewcart.php
+++ b/includes/class-gtm-server-side-event-viewcart.php
@@ -34,6 +34,9 @@ public function init() {
 	 * @return void
 	 */
 	public function wp_footer() {
+		if ( ! GTM_Server_Side_Helpers::can_output_sensitive_data() ) {
+			return;
+		}
 		if ( ! is_cart() ) {
 			return;
 		}
@@ -56,9 +59,10 @@ public function wp_footer() {
 			),
 		);
 
-		if ( GTM_Server_Side_WC_Helpers::instance()->is_enable_user_data() ) {
+		if ( GTM_Server_Side_WC_Helpers::instance()->should_output_user_data() ) {
 			$data_layer['user_data'] = GTM_Server_Side_WC_Helpers::instance()->get_data_layer_user_data();
 		}
+		echo GTM_SENSITIVE_DATA_NOTICE; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 		?>
 		<script type="text/javascript">
 			dataLayer.push( { ecommerce: null } );
diff --git a/includes/class-gtm-server-side-event-viewitem.php b/includes/class-gtm-server-side-event-viewitem.php
index 7a64d6b..34364a8 100644
--- a/includes/class-gtm-server-side-event-viewitem.php
+++ b/includes/class-gtm-server-side-event-viewitem.php
@@ -56,8 +56,9 @@ public function wp_footer() {
 			),
 		);
 
-		if ( GTM_Server_Side_WC_Helpers::instance()->is_enable_user_data() ) {
+		if ( GTM_Server_Side_WC_Helpers::instance()->should_output_user_data() ) {
 			$data_layer['user_data'] = GTM_Server_Side_WC_Helpers::instance()->get_data_layer_user_data();
+			echo GTM_SENSITIVE_DATA_NOTICE; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 		}
 		?>
 		<script type="text/javascript">
diff --git a/includes/class-gtm-server-side-event-viewitemlist.php b/includes/class-gtm-server-side-event-viewitemlist.php
index 6a59c55..6d52456 100644
--- a/includes/class-gtm-server-side-event-viewitemlist.php
+++ b/includes/class-gtm-server-side-event-viewitemlist.php
@@ -52,8 +52,9 @@ public function wp_footer() {
 			),
 		);
 
-		if ( GTM_Server_Side_WC_Helpers::instance()->is_enable_user_data() ) {
+		if ( GTM_Server_Side_WC_Helpers::instance()->should_output_user_data() ) {
 			$data_layer['user_data'] = GTM_Server_Side_WC_Helpers::instance()->get_data_layer_user_data();
+			echo GTM_SENSITIVE_DATA_NOTICE; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 		}
 		?>
 		<script type="text/javascript">
diff --git a/includes/class-gtm-server-side-frontend-assets.php b/includes/class-gtm-server-side-frontend-assets.php
index 5cacdfc..6275442 100644
--- a/includes/class-gtm-server-side-frontend-assets.php
+++ b/includes/class-gtm-server-side-frontend-assets.php
@@ -42,8 +42,9 @@ public function wp_enqueue_scripts() {
 			'DATA_LAYER_CUSTOM_EVENT_NAME' => GTM_SERVER_SIDE_DATA_LAYER_CUSTOM_EVENT_NAME,
 		);
 
-		if ( GTM_Server_Side_WC_Helpers::instance()->is_enable_user_data() ) {
+		if ( GTM_Server_Side_WC_Helpers::instance()->should_output_user_data() ) {
 			$scripts['user_data'] = GTM_Server_Side_WC_Helpers::instance()->get_data_layer_user_data();
+			echo GTM_SENSITIVE_DATA_NOTICE; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 		}
 
 		wp_localize_script( 'gtm-server-side', 'varGtmServerSide', $scripts );
diff --git a/includes/class-gtm-server-side-helpers.php b/includes/class-gtm-server-side-helpers.php
index 67d0512..021ea6b 100644
--- a/includes/class-gtm-server-side-helpers.php
+++ b/includes/class-gtm-server-side-helpers.php
@@ -55,6 +55,13 @@ class GTM_Server_Side_Helpers {
 	 */
 	private static $is_stape_analytics_support;
 
+	/**
+	 * Cache detection result.
+	 *
+	 * @var bool|null
+	 */
+	private static $is_page_cached;
+
 	/**
 	 * Get attr option.
 	 *
@@ -620,4 +627,26 @@ public static function get_cache_field( $key, $callback ) {
 	public static function delete_cache_field( $key ) {
 		delete_transient( $key . '__generated' );
 	}
+
+	/**
+	 * Check if the current page is cached.
+	 *
+	 * @return bool
+	 */
+	public static function is_page_cached() {
+		if ( null === static::$is_page_cached ) {
+			static::$is_page_cached = apply_filters( 'gtm_server_side_is_page_cached', false );
+		}
+
+		return static::$is_page_cached;
+	}
+
+	/**
+	 * Check if sensitive data can be output (not on cached pages).
+	 *
+	 * @return bool
+	 */
+	public static function can_output_sensitive_data() {
+		return ! static::is_page_cached();
+	}
 }
diff --git a/includes/class-gtm-server-side-wc-helpers.php b/includes/class-gtm-server-side-wc-helpers.php
index fc99f24..d384ac5 100644
--- a/includes/class-gtm-server-side-wc-helpers.php
+++ b/includes/class-gtm-server-side-wc-helpers.php
@@ -410,6 +410,15 @@ public function is_enable_user_data() {
 		return function_exists( 'WC' ) && ( WC()->customer instanceof WC_Customer ) && GTM_Server_Side_Helpers::is_enable_data_layer_user_data();
 	}
 
+	/**
+	 * Check if user data can be output (considering cache protection).
+	 *
+	 * @return bool
+	 */
+	public function should_output_user_data() {
+		return $this->is_enable_user_data() && GTM_Server_Side_Helpers::can_output_sensitive_data();
+	}
+
 	/**
 	 * Return formatted price
 	 *