diff --git a/projects/plugins/boost/app/assets/src/js/features/page-cache/meta/meta.tsx b/projects/plugins/boost/app/assets/src/js/features/page-cache/meta/meta.tsx
index 258295749a697..6c4f2bacdb7b0 100644
--- a/projects/plugins/boost/app/assets/src/js/features/page-cache/meta/meta.tsx
+++ b/projects/plugins/boost/app/assets/src/js/features/page-cache/meta/meta.tsx
@@ -157,6 +157,24 @@ const BypassPatterns = ( {
 	// @todo - add proper link.
 	const exclusionsLink = 'https://jetpack.com';
 
+	const validateInputValue = ( value: string ) => {
+		setInputValue( value );
+		setInputInvalid( ! validatePatterns( value ) );
+	}
+
+	const validatePatterns = ( value: string ) => {
+		const lines = value.split( '\n' ).map( line => line.trim() ).filter( line => line.trim() !== '' );
+
+		// check if it's a valid regex
+		try {
+			lines.forEach( line => new RegExp( line ) );
+		} catch ( e ) {
+			return false;
+		}
+
+		return true;
+	}
+
 	useEffect( () => {
 		setInputValue( patterns );
 	}, [ patterns ] );
@@ -182,7 +200,7 @@ const BypassPatterns = ( {
 			<textarea
 				value={ inputValue }
 				rows={ 3 }
-				onChange={ e => setInputValue( e.target.value ) }
+				onChange={ e => validateInputValue( e.target.value ) }
 				id="jb-cache-exceptions"
 			/>
 			<p className={ classNames( styles.description, styles[ 'error-message' ] ) }>
@@ -212,7 +230,7 @@ const BypassPatterns = ( {
 					{ __( 'An error occurred while saving changes. Please, try again.', 'jetpack-boost' ) }
 				</Notice>
 			) }
-			<Button disabled={ patterns === inputValue } onClick={ save } className={ styles.button }>
+			<Button disabled={ patterns === inputValue || inputInvalid } onClick={ save } className={ styles.button }>
 				{ __( 'Save', 'jetpack-boost' ) }
 			</Button>
 		</div>
diff --git a/projects/plugins/boost/app/modules/optimizations/page-cache/data-sync/Page_Cache_Entry.php b/projects/plugins/boost/app/modules/optimizations/page-cache/data-sync/Page_Cache_Entry.php
index 2a8ee03f98d45..4e25efb74c161 100644
--- a/projects/plugins/boost/app/modules/optimizations/page-cache/data-sync/Page_Cache_Entry.php
+++ b/projects/plugins/boost/app/modules/optimizations/page-cache/data-sync/Page_Cache_Entry.php
@@ -27,19 +27,72 @@ public function set( $value ) {
 	}
 
 	/**
-	 * Sanitizes the given value, ensuring that it is a comma-separated list of unique, trimmed strings.
+	 * Sanitizes the given value, ensuring that it is list of valid patterns.
 	 *
 	 * @param mixed $value The value to sanitize.
 	 *
-	 * @return string The sanitized value, as a comma-separated list of unique, trimmed strings.
+	 * @return string The sanitized value, as a list.
 	 */
 	private function sanitize_value( $value ) {
 		if ( is_array( $value ) ) {
-			$value = array_values( array_unique( array_filter( array_map( 'trim', $value ) ) ) );
+			$value = array_values( array_unique( array_filter( array_map( 'trim', array_map( 'strtolower', $value ) ) ) ) );
+
+			$home_url = home_url( '/' );
+
+			foreach ( $value as &$path ) {
+				// Strip home URL (both secure and non-secure).
+				$path = str_ireplace(
+					array(
+						$home_url,
+						str_replace( 'http:', 'https:', $home_url ),
+					),
+					array(
+						'/',
+						'/',
+					),
+					$path
+				);
+
+				// Remove double shashes.
+				$path = str_replace( '//', '/', $path );
+
+				// Make sure there's a leading slash.
+				$path = '/' . ltrim( $path, '/' );
+
+				// Fix up any wildcards.
+				$path = $this->sanitize_wildcards( $path );
+			}
 		} else {
 			$value = array();
 		}
 
 		return $value;
 	}
+
+	/**
+	 * Sanitize wildcards in a given path.
+	 *
+	 * @param string $path The path to sanitize.
+	 * @return string The sanitized path.
+	 */
+	private function sanitize_wildcards( $path ) {
+		if ( ! $path ) {
+			return '';
+		}
+
+		$path_components = explode( '/', $path );
+		$arr             = array(
+			'.*'   => '(.*)',
+			'*'    => '(.*)',
+			'(*)'  => '(.*)',
+			'(.*)' => '(.*)',
+		);
+
+		foreach ( $path_components as &$path_component ) {
+			$path_component = strtr( $path_component, $arr );
+		}
+		$path = implode( '/', $path_components );
+
+		return $path;
+	}
 }
diff --git a/projects/plugins/boost/changelog/update-cache-ui-invalid-exceptions-feedback b/projects/plugins/boost/changelog/update-cache-ui-invalid-exceptions-feedback
new file mode 100644
index 0000000000000..0a4fd402d053a
--- /dev/null
+++ b/projects/plugins/boost/changelog/update-cache-ui-invalid-exceptions-feedback
@@ -0,0 +1,5 @@
+Significance: patch
+Type: added
+Comment: Update cache exceptions UI to show an error if there's an invalid pattern.
+
+