Can I use
?

CSS Variables (Custom Properties)

- CR

Permits the declaration and usage of cascading variables in stylesheets.

Chrome

  1. 4 - 47: Not supported
  2. 48: Disabled by default
  3. 49 - 105: Supported
  4. 106: Supported
  5. 107 - 109: Supported

Edge

  1. 12 - 14: Not supported
  2. 15: Partial support
  3. 16 - 104: Supported
  4. 105: Supported

Safari

  1. 3.1 - 9: Not supported
  2. 9.1: Partial support
  3. 10 - 15.6: Supported
  4. 16.0: Supported
  5. 16.1 - TP: Supported

Firefox

  1. 2 - 30: Not supported
  2. 31 - 104: Supported
  3. 105: Supported
  4. 106 - 107: Supported

Opera

  1. 9 - 34: Not supported
  2. 35: Disabled by default
  3. 36 - 90: Supported
  4. 91: Supported

IE

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

Chrome for Android

  1. 105: Supported

Safari on iOS

  1. 3.2 - 9.2: Not supported
  2. 9.3: Partial support
  3. 10 - 15.6: Supported
  4. 16.0: Supported
  5. 16.1: Supported

Samsung Internet

  1. 4: Not supported
  2. 5 - 17.0: Supported
  3. 18.0: Supported

Opera Mini

  1. all: Not supported

Opera Mobile

  1. 10 - 12.1: Not supported
  2. 64: Supported

UC Browser for Android

  1. 13.4: Supported

Android Browser

  1. 2.1 - 4.4.4: Not supported
  2. 105: Supported

Firefox for Android

  1. 104: Supported

QQ Browser

  1. 13.1: Supported

Baidu Browser

  1. 13.18: Supported

KaiOS Browser

  1. 2.5: Supported
Resources:
Edge Dev Blog post
MDN Web Docs - Using CSS variables
Polyfill for IE11
Mozilla hacks article (older syntax)