CSS Generated content for pseudo-elements

- REC

Method of displaying text or images before or after the given element's contents using the ::before and ::after pseudo-elements. All browsers with support also support the attr() notation in the content property.

IE

  1. 5.5 - 7
  2. 8
  3. 9 - 10
  4. 11

Edge

  1. 12 - 81
  2. 83

Firefox

  1. 2 - 77
  2. 78
  3. 79 - 80

Chrome

  1. 4 - 81
  2. 83
  3. 84 - 86

Safari

  1. 3.1 - 13
  2. 13.1
  3. 14 - TP

Opera

  1. 9 - 68
  2. 69

iOS Safari

  1. 3.2 - 13.3
  2. 13.4
  3. 14.0

Opera Mini

  1. all

Android Browser

  1. 2.1 - 4.4.4
  2. 81

Blackberry Browser

  1. 7
  2. 10

Opera Mobile

  1. 10 - 12.1
  2. 46

Chrome for Android

  1. 81

Firefox for Android

  1. 68

IE Mobile

  1. 10
  2. 11

UC Browser for Android

  1. 12.12

Samsung Internet

  1. 4 - 11.2
  2. 12.0

QQ Browser

  1. 10.4

Baidu Browser

  1. 7.12

KaiOS Browser

  1. 2.5

For content to appear in pseudo-elements, the content property must be set (but may be an empty string).

Resources:
Guide on usage
Dev.Opera article
WebPlatform Docs