Post

The CloseWatcher API landed in Firefox 149, making it easy to listen for platform-specific 'dismiss' signals. Here's how it works:

Mihkel Eidast

@mihkel.eida.st

25 Mar

Is there any way to polyfill this?

Luke

@lukewarlow.dev

I think mostly yes, the anti-abuse mechanics would be difficult (impossible?) but then also not really important because a polyfill couldn't handle the Android back gesture.

25/3/26, 7:44 pm1 repost1 like

Mihkel Eidast

@mihkel.eida.st

25 Mar

Yeah I'm mostly interested in just that - polyfilling the browser / gesture back action.

Luke

@lukewarlow.dev

25 Mar

Yeah that's essentially not possible. You *might* be able to do something very hacky with the navigation API and intercepting back navigations but I'm not sure how much that's exposed.

Firefox for Web Developers

@webdevs.firefox.com

26 Mar

Yeah, it seems tricky because, if you do a push navigation, escape should still do closewatcher things first. So, it's like a different layer on top of navigation. Also, the polyfill would mess with the back button.