See Compatibility#Browser support matrix (mobile) for the source of truth of the supported browsers on mobile, and Compatibility#Browser support matrix for the supported browsers on desktop.
Suggested testing (where applicable), RTL+LTR, portrait+landscape, phone & tablet devices.
Updated March 2017
Modern experience
edit- iOS 8+
- Mobile Safari 8+
- Android 4+
- Chrome 48+
- Chrome 43+
- Android Browser 4
Basic experience
edit- Android 2
- UC browser (not mini with compression)
- UC Mini (with compression)
- Opera Mini compressed ("Extreme" mode on Android)
- Opera Mini non-compressed (not extreme mode)
- Android 2.3 Web Browser
- iOS 6, 7
- Opera Mini compressed ("Opera Mini" mode on iOS)
- iOS 6 Safari
- iOS 7 Safari
- Windows 8 and 10
- Mobile IE