Can I use
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rem (root em) units

- CR

Type of unit similar to em, but relative only to the root element, not any parent element. Thus compounding does not occur as it does with em units.

Chrome

  1. 4 - 116: Supported
  2. 117: Supported
  3. 118 - 120: Supported

Edge

  1. 12 - 116: Supported
  2. 117: Supported

Safari

  1. 3.1 - 4: Not supported
  2. 5 - 16.6: Supported
  3. 17.0: Supported
  4. 17.1 - TP: Supported

Firefox

  1. 2 - 3.5: Not supported
  2. 3.6 - 116: Supported
  3. 117: Supported
  4. 118 - 120: Supported

Opera

  1. 9 - 11.5: Not supported
  2. 11.6 - 101: Supported
  3. 102: Supported

IE

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

Chrome for Android

  1. 117: Supported

Safari on iOS

  1. 3.2: Not supported
  2. 4 - 4.3: Supported
  3. 5: Partial support
  4. 6 - 16.6: Supported
  5. 17.0: Supported
  6. 17.1: Supported

Samsung Internet

  1. 4 - 21: Supported
  2. 22: Supported

Opera Mini

  1. all: Supported

Opera Mobile

  1. 10 - 11.5: Not supported
  2. 12 - 12.1: Supported
  3. 73: Supported

UC Browser for Android

  1. 15.5: Supported

Android Browser

  1. 2.1 - 4.4.4: Supported
  2. 117: Supported

Firefox for Android

  1. 117: Supported

QQ Browser

  1. 13.1: Supported

Baidu Browser

  1. 13.18: Supported

KaiOS Browser

  1. 2.5: Supported
  2. 3: Supported
Resources:
REM Polyfill
Article on usage