CSS3 Box-sizing

- WD

Method of specifying whether or not an element's borders and padding should be included in size units

Chrome

  1. 4 - 9: Supported
  2. 10 - 121: Supported
  3. 122: Supported
  4. 123 - 125: Supported

Edge

  1. 12 - 121: Supported
  2. 122: Supported

Safari

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

Firefox

  1. 2 - 28: Supported
  2. 29 - 122: Supported
  3. 123: Supported
  4. 124 - 126: Supported

Opera

  1. 9: Not supported
  2. 9.5 - 107: Supported
  3. 108: Supported

IE

  1. 5.5 - 7: Not supported (but has polyfill available)
  2. 8 - 10: Supported
  3. 11: Supported

Chrome for Android

  1. 122: Supported

Safari on iOS

  1. 3.2 - 4.3: Supported
  2. 5 - 17.3: Supported
  3. 17.4: Supported

Samsung Internet

  1. 4 - 22: Supported
  2. 23: Supported

Opera Mini

  1. all: Supported

Opera Mobile

  1. 10 - 12.1: Supported
  2. 80: Supported

UC Browser for Android

  1. 15.5: Supported

Android Browser

  1. 2.1 - 3: Supported
  2. 4 - 4.4.4: Supported
  3. 122: Supported

Firefox for Android

  1. 123: Supported

QQ Browser

  1. 14.9: Supported

Baidu Browser

  1. 13.52: Supported

KaiOS Browser

  1. 2.5: Supported
  2. 3: Supported

Firefox versions before 57 also supported the padding-box value for box-sizing, though this value was been removed from the specification and later versions of the browser.

Resources:
CSS Tricks
MDN Web Docs - CSS box-sizing
Polyfill for IE
WebPlatform Docs
Blog post