Declares a variable with block level scope

IE

  1. 5.5 - 10
  2. 11

Edge

  1. 12 - 81
  2. 83

Firefox

  1. 2 - 43
  2. 44 - 77
  3. 78
  4. 79 - 80

Chrome

  1. 4 - 18
  2. 19 - 40
  3. 41 - 48
  4. 49 - 81
  5. 83
  6. 84 - 86

Safari

  1. 3.1 - 9.1
  2. 10 - 10.1
  3. 11 - 13
  4. 13.1
  5. 14 - TP

Opera

  1. 9 - 12.1
  2. 15 - 27
  3. 28 - 35
  4. 36 - 68
  5. 69

iOS Safari

  1. 3.2 - 9.3
  2. 10 - 10.3
  3. 11 - 13.3
  4. 13.4
  5. 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
  2. 5 - 11.2
  3. 12.0

QQ Browser

  1. 10.4

Baidu Browser

  1. 7.12

KaiOS Browser

  1. 2.5
Resources:
MDN Web Docs - let
Variables and Constants in ES6