Online/offline status

- LS

Events to indicate when the user's connected (online and offline events) and the navigator.onLine property to see current status.

IE

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

Edge

  1. 12 - 81
  2. 83

Firefox

  1. 2 - 3
  2. 3.5 - 3.6
  3. 4 - 40
  4. 41 - 75
  5. 76
  6. 77 - 78

Chrome

  1. 4 - 13
  2. 14 - 81
  3. 83
  4. 84 - 86

Safari

  1. 3.1 - 4
  2. 5 - 13
  3. 13.1
  4. TP

Opera

  1. 9 - 12
  2. 12.1
  3. 15 - 67
  4. 68

iOS Safari

  1. 3.2 - 4.1
  2. 4.2 - 13.3
  3. 13.4

Opera Mini

  1. all

Android Browser

  1. 2.1 - 2.2
  2. 2.3 - 4.4.4
  3. 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 - 10.1
  2. 11.1

QQ Browser

  1. 10.4

Baidu Browser

  1. 7.12

KaiOS Browser

  1. 2.5

"online" does not always mean connection to the internet, it can also just mean connection to some network.

Early versions of Chrome and Safari always reported "true" for navigator.onLine

Resources:
MDN Web Docs - NavigatorOnLine.onLine