display: run-in

- WD

If the run-in box contains a block box, same as block. If a block box follows the run-in box, the run-in box becomes the first inline box of the block box. If an inline box follows, the run-in box becomes a block box.

IE

  1. 5.5 - 7: Not supported
  2. 8 - 10: Supported
  3. 11: Supported

Edge

  1. 12 - 89: Not supported
  2. 90: Not supported

Firefox

  1. 2 - 86: Not supported
  2. 87: Not supported
  3. 88 - 89: Not supported

Chrome

  1. 4 - 31: Supported
  2. 32 - 89: Not supported
  3. 90: Not supported
  4. 91 - 93: Not supported

Safari

  1. 3.1 - 4: Supported
  2. 5 - 6: Supported
  3. 6.1: Support unknown
  4. 7 - 13.1: Not supported
  5. 14: Not supported
  6. TP: Not supported

Opera

  1. 9 - 18: Supported
  2. 19 - 72: Not supported
  3. 73: Not supported

Safari on iOS

  1. 3.2: Supported
  2. 4 - 7.1: Supported
  3. 8 - 13.7: Not supported
  4. 14: Not supported

Opera Mini

  1. all: Supported

Android Browser

  1. 2.1 - 4.4: Supported
  2. 4.4.3: Not supported
  3. 89: Not supported

Opera Mobile

  1. 10 - 12.1: Supported
  2. 62: Not supported

Chrome for Android

  1. 89: Not supported

Firefox for Android

  1. 86: Not supported

UC Browser for Android

  1. 12.12: Not supported

Samsung Internet

  1. 4 - 12.0: Not supported
  2. 13.0: Not supported

QQ Browser

  1. 10.4: Not supported

Baidu Browser

  1. 7.12: Not supported

KaiOS Browser

  1. 2.5: Not supported
Resources:
Mozilla bug report
CSS Tricks article