Send mouse back/forward buttons to javascript
User input
 
Web pages can now process mouse events (mousedown, auxclick, mouseup) for back and forward buttons on mice with five or more buttons. This allows back and forward mouse buttons to be prevented by applications that wish to override them. For example they may be useful for games.

Documentation
https://github.com/w3c/pointerevents/issues/191
Specification
Established standard

Status in Chromium
Blink components: Blink>Input


Enabled by default (tracking bug) in:

Chrome for desktop release 67
Chrome for Android release 67
Android WebView release 67
Opera release 54
Opera for Android release 54
Consensus & Standardization
After a feature ships in Chrome, the values listed here are not guaranteed to be up to date.

Firefox:
No public signals
Edge:
No public signals
Safari:
No public signals
Web Developers:
Positive
Owner
dtapuska@chromium.org
Last updated on 2018-04-12

STOP THIS. The back button is for navigation.