CSS position:sticky

- WD

Keeps elements positioned as "fixed" or "relative" depending on how it appears in the viewport. As a result the element is "stuck" when necessary while scrolling.

IE

  1. 5.5 - 10: Not supported
  2. 11: Not supported

Edge

  1. 12 - 15: Not supported
  2. 16 - 18: Partial support
  3. 79 - 90: Partial support
  4. 91 - 102: Supported
  5. 103: Supported

Firefox

  1. 2 - 25: Not supported
  2. 26 - 31: Disabled by default
  3. 32 - 58: Partial support
  4. 59 - 101: Supported
  5. 102: Supported
  6. 103 - 104: Supported

Chrome

  1. 4 - 22: Not supported
  2. 23 - 36: Disabled by default
  3. 37 - 51: Not supported
  4. 52 - 55: Disabled by default
  5. 56 - 90: Partial support
  6. 91 - 102: Supported
  7. 103: Supported
  8. 104 - 106: Supported

Safari

  1. 3.1 - 6: Not supported
  2. 6.1 - 7: Partial support
  3. 7.1 - 12.1: Supported
  4. 13 - 15.4: Supported
  5. 15.5: Supported
  6. 16.0 - TP: Supported

Opera

  1. 9 - 38: Not supported
  2. 39 - 41: Disabled by default
  3. 42 - 77: Partial support
  4. 78 - 85: Supported
  5. 86: Supported
  6. 87: Supported

Safari on iOS

  1. 3.2 - 5.1: Not supported
  2. 6 - 7.1: Partial support
  3. 8 - 12.5: Supported
  4. 13 - 15.4: Supported
  5. 15.5: Supported
  6. 16.0: Supported

Opera Mini

  1. all: Not supported

Android Browser

  1. 2.1 - 4.4.4: Not supported
  2. 103: Supported

Opera Mobile

  1. 10 - 12.1: Not supported
  2. 64: Supported

Chrome for Android

  1. 103: Supported

Firefox for Android

  1. 101: Supported

UC Browser for Android

  1. 12.12: Partial support

Samsung Internet

  1. 4 - 5.4: Not supported
  2. 6.2 - 16.0: Supported
  3. 17.0: Supported

QQ Browser

  1. 10.4: Partial support

Baidu Browser

  1. 7.12: Not supported

KaiOS Browser

  1. 2.5: Partial support

Any ancestor between the sticky element and its user-scrollable container with overflow computed as anything but visible/clip will effectively prevent sticking behavior.

Resources:
MDN Web Docs - CSS position
HTML5Rocks
Polyfill
Another polyfill
geddski article: Examples and Gotchas
WebPlatform Docs