CSS Flexible Box Layout Module

- CR

Method of positioning elements in horizontal or vertical stacks. Support includes all properties prefixed with flex, as well as display: flex, display: inline-flex, align-content, align-items, align-self, justify-content and order.

IE

  1. 5.5 - 9: Not supported
  2. 10: Partial support
  3. 11: Partial support

Edge

  1. 12 - 85: Supported
  2. 86: Supported

Firefox

  1. 2 - 21: Partial support
  2. 22 - 27: Partial support
  3. 28 - 80: Supported
  4. 81: Supported
  5. 82 - 83: Supported

Chrome

  1. 4 - 20: Partial support
  2. 21 - 28: Supported
  3. 29 - 85: Supported
  4. 86: Supported
  5. 87 - 89: Supported

Safari

  1. 3.1 - 6: Partial support
  2. 6.1 - 8: Supported
  3. 9 - 13.1: Supported
  4. 14: Supported
  5. TP: Supported

Opera

  1. 9 - 12: Not supported
  2. 12.1: Supported
  3. 15 - 16: Supported
  4. 17 - 70: Supported
  5. 71: Supported

iOS Safari

  1. 3.2 - 6.1: Partial support
  2. 7 - 8.4: Supported
  3. 9 - 13.7: Supported
  4. 14: Supported

Opera Mini

  1. all: Supported

Android Browser

  1. 2.1 - 4.3: Partial support
  2. 4.4 - 4.4.4: Supported
  3. 81: Supported

Blackberry Browser

  1. 7: Partial support
  2. 10: Supported

Opera Mobile

  1. 10 - 12: Not supported
  2. 12.1: Supported
  3. 59: Supported

Chrome for Android

  1. 85: Supported

Firefox for Android

  1. 79: Supported

IE Mobile

  1. 10: Partial support
  2. 11: Supported

UC Browser for Android

  1. 12.12: Supported

Samsung Internet

  1. 4 - 11.2: Supported
  2. 12.0: Supported

QQ Browser

  1. 10.4: Supported

Baidu Browser

  1. 7.12: Supported

KaiOS Browser

  1. 2.5: Supported

Most partial support refers to supporting an older version of the specification or an older syntax.

Resources:
Flexbox CSS generator
A Complete Guide to Flexbox
Tutorial on cross-browser support
10up Open Sources IE 8 and 9 Support for Flexbox
Flexbugs: Repo for flexbox bugs
Ecligrid - Mobile first flexbox grid system
The Difference Between Width and Flex-Basis
Examples on how to solve common layout problems with flexbox
Flexbox playground and code generator
Article on using the latest spec
Sub-features:
gap property for Flexbox