The 404_error non-interaction event fires whenever the user hits a page on your website that returns a 404 code ( is unavailable ).

Parameters

Utilization

You can use this event to discover pages of your website that are reachable in some way, but have no content. If the page is a landing page ( has an external referrer ), then you have an external platform that contains a broken link. If the referrer is an internal page of your wesite, then the broken link is self-hosted. Either case, armed with this knowledge, now you can take action to remove the broken link or add content to serve users a better experience.