tabindex global attribute

- LS

Specifies the focusability of the element and in what order (if any) it should become focused (relative to other elements) when "tabbing" through the document.

Chrome

  1. 4 - 14: Support unknown
  2. 15 - 125: Supported
  3. 126: Supported
  4. 127 - 129: Supported

Edge

  1. 12 - 125: Supported
  2. 126: Supported

Safari

  1. 3.1 - 5: Support unknown
  2. 5.1 - 17.4: Supported
  3. 17.5: Supported
  4. 17.6 - TP: Supported

Firefox

  1. 2 - 3.6: Support unknown
  2. 4 - 127: Supported
  3. 128: Supported
  4. 129 - 131: Supported

Opera

  1. 9: Support unknown
  2. 9.5 - 110: Supported
  3. 111: Supported

IE

  1. 5.5 - 6: Support unknown
  2. 7 - 10: Supported
  3. 11: Supported

Chrome for Android

  1. 126: Supported

Safari on iOS

  1. 3.2 - 17.4: Supported
  2. 17.5: Supported
  3. 17.6 - 18.0: Supported

Samsung Internet

  1. 4 - 24: Support unknown
  2. 25: Support unknown

Opera Mini

  1. all: Support unknown

Opera Mobile

  1. 10 - 12.1: Support unknown
  2. 80: Supported

UC Browser for Android

  1. 15.5: Supported

Android Browser

  1. 2.1 - 4.4.4: Support unknown
  2. 126: Support unknown

Firefox for Android

  1. 127: Supported

QQ Browser

  1. 14.9: Supported

Baidu Browser

  1. 13.52: Supported

KaiOS Browser

  1. 2.5: Supported
  2. 3: Supported

Mac OS X "Full Keyboard Access" refers to setting Keyboard→Shortcuts→Full Keyboard Access to "All controls" in the System Preferences.

"Unknown" support for mobile browsers is due to lacking a method of tabbing through fields.

Resources:
MDN Web Docs - tabindex attribute