CSS user-select: none

- WD

Method of preventing text/element selection using CSS.

IE

  1. 8
  2. 9
  3. 10
  4. 11

Edge

  1. 12
  2. 13
  3. 14
  4. 15
  5. 16

Firefox

  1. 51
  2. 52
  3. 53
  4. 54
  5. 55
  6. 56
  7. 57

Chrome

  1. 56
  2. 57
  3. 58
  4. 59
  5. 60
  6. 61
  7. 62

Safari

  1. 9
  2. 9.1
  3. 10
  4. 10.1
  5. 11
  6. TP

Opera

  1. 43
  2. 44
  3. 45
  4. 46
  5. 47
  6. 48

iOS Safari

  1. 9.0-9.2
  2. 9.3
  3. 10.0-10.2
  4. 10.3
  5. 11

Opera Mini

  1. all

Android Browser

  1. 4.2-4.3
  2. 4.4
  3. 4.4.3-4.4.4
  4. 56

Blackberry Browser

  1. 7
  2. 10

Opera Mobile

  1. 11.5
  2. 12
  3. 12.1
  4. 37

Chrome for Android

  1. 59

Firefox for Android

  1. 54

IE Mobile

  1. 10
  2. 11

UC Browser for Android

  1. 11.4

Samsung Internet

  1. 4
  2. 5

QQ Browser

  1. 1.2

Baidu Browser

  1. 7.12
Resources:
CSS Tricks article
MSDN Documentation
Mozilla Developer Network (MDN) documentation - CSS user-select