KeyboardEvent.key

- WD

A KeyboardEvent property whose value is a string identifying the key that was pressed. Covers character keys, non-character keys (e.g. arrow keys), and dead keys.

IE

  1. 5.5 - 8: Not supported
  2. 9 - 10: Partial support
  3. 11: Partial support

Edge

  1. 12 - 18: Partial support
  2. 79 - 85: Supported
  3. 86: Supported

Firefox

  1. 2 - 22: Not supported
  2. 23 - 28: Partial support
  3. 29 - 80: Supported
  4. 81: Supported
  5. 82 - 83: Supported

Chrome

  1. 4 - 50: Not supported
  2. 51 - 85: Supported
  3. 86: Supported
  4. 87 - 89: Supported

Safari

  1. 3.1 - 10: Not supported
  2. 10.1 - 13.1: Supported
  3. 14: Supported
  4. TP: Supported

Opera

  1. 9 - 11.6: Not supported
  2. 12: Support unknown
  3. 12.1: Supported
  4. 15 - 37: Not supported
  5. 38 - 70: Supported
  6. 71: Supported

iOS Safari

  1. 3.2 - 10.2: Not supported
  2. 10.3 - 13.7: Supported
  3. 14: Supported

Opera Mini

  1. all: Supported

Android Browser

  1. 2.1 - 4.4.4: Not supported
  2. 81: Supported

Blackberry Browser

  1. 7: Not supported
  2. 10: Not supported

Opera Mobile

  1. 10 - 11.5: Not supported
  2. 12: Support unknown
  3. 12.1: Supported
  4. 59: Support unknown

Chrome for Android

  1. 85: Supported

Firefox for Android

  1. 79: Supported

IE Mobile

  1. 10: Partial support
  2. 11: Partial support

UC Browser for Android

  1. 12.12: Supported

Samsung Internet

  1. 4: Not supported
  2. 5 - 11.2: Supported
  3. 12.0: Supported

QQ Browser

  1. 10.4: Not supported

Baidu Browser

  1. 7.12: Not supported

KaiOS Browser

  1. 2.5: Supported

"Some key events, or their values, might be suppressed by the IME in use". On mobile (virtual keyboard), for every key Blink and WebKit based browsers report "Unidentified", Gecko reports "Process".

Resources:
WebKit feature request bug
Chrome tracking bug
Edge bug report
MDN Web Docs - key
shim-keyboard-event-key: shim for non-standard key identifiers for IE & Edge
Spec listing all key string values