Navigation to unknown protocol will be blocked


Categories: DOM

Releases: Firefox 76, Firefox 78 ESR


Previously, Firefox was showing an error page saying “The address wasn’t understood” when a web page attempted to navigate to an unknown protocol using location.href, <meta http-equiv="refresh"> or similar method. This behaviour had caused an user experience issue on various sites that tried to open their own external application.

Starting with Firefox 76, such page navigations/redirects will be ignored like Google Chrome, and Web Console will log a warning: “Prevented navigation to … due to an unknown protocol.”

If you need to launch an external application or simply check if an external application is installed, you can instead use either or an <iframe>.