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 - 121: Supported
  3. 122: Supported
  4. 123 - 125: Supported

Edge

  1. 12 - 120: Supported
  2. 121: Supported

Safari

  1. 3.1 - 5: Support unknown
  2. 5.1 - 17.2: Supported
  3. 17.3: Supported
  4. 17.4 - TP: Supported

Firefox

  1. 2 - 3.6: Support unknown
  2. 4 - 122: Supported
  3. 123: Supported
  4. 124 - 126: Supported

Opera

  1. 9: Support unknown
  2. 9.5 - 105: Supported
  3. 106: Supported

IE

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

Chrome for Android

  1. 121: Supported

Safari on iOS

  1. 3.2 - 17.2: Supported
  2. 17.3: Supported
  3. 17.4: Supported

Samsung Internet

  1. 4 - 22: Support unknown
  2. 23: Support unknown

Opera Mini

  1. all: Support unknown

Opera Mobile

  1. 10 - 12.1: Support unknown
  2. 73: Supported

UC Browser for Android

  1. 15.5: Supported

Android Browser

  1. 2.1 - 4.4.4: Support unknown
  2. 121: Support unknown

Firefox for Android

  1. 122: Supported

QQ Browser

  1. 13.1: Supported

Baidu Browser

  1. 13.18: 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