#rrggbbaa hex color notation

- CR

The CSS Color Module Level 4 defines new 4 & 8 character hex notation for color to include the opacity level.

Chrome

  1. 4 - 51: Not supported
  2. 52 - 61: Disabled by default
  3. 62 - 125: Supported
  4. 126: Supported
  5. 127 - 129: Supported

Edge

  1. 12 - 18: Not supported
  2. 79 - 124: Supported
  3. 125: Supported

Safari

  1. 3.1 - 9.1: Not supported
  2. 10 - 17.4: Supported
  3. 17.5: Supported
  4. 17.6 - TP: Supported

Firefox

  1. 2 - 48: Not supported
  2. 49 - 126: Supported
  3. 127: Supported
  4. 128 - 130: Supported

Opera

  1. 9 - 38: Not supported
  2. 39 - 51: Disabled by default
  3. 52 - 109: Supported
  4. 110: Supported

IE

  1. 5.5 - 10: Not supported
  2. 11: Not supported

Chrome for Android

  1. 125: Supported

Safari on iOS

  1. 3.2 - 9.3: Not supported
  2. 10 - 17.4: Supported
  3. 17.5: Supported
  4. 17.6 - 18.0: Supported

Samsung Internet

  1. 4: Not supported
  2. 5 - 7.4: Disabled by default
  3. 8.2 - 24: Supported
  4. 25: Supported

Opera Mini

  1. all: Not supported

Opera Mobile

  1. 10 - 12.1: Not supported
  2. 80: Supported

UC Browser for Android

  1. 15.5: Supported

Android Browser

  1. 2.1 - 4.4.4: Not supported
  2. 125: Supported

Firefox for Android

  1. 126: Supported

QQ Browser

  1. 14.9: Supported

Baidu Browser

  1. 13.52: Supported

KaiOS Browser

  1. 2.5: Not supported
  2. 3: Supported

Only supported in Android WebViews in apps that target Android Pie, due to this issue

Resources:
JS Bin testcase