Can I use
?

seamless attribute for iframes

- UNOFF

The seamless attribute makes an iframe's contents actually part of a page, and adopts the styles from its hosting page. The attribute has been removed from both the WHATWG and the W3C HTML5 specifications.

Chrome

  1. 4 - 19: Not supported
  2. 20 - 26: Disabled by default
  3. 27 - 112: Not supported
  4. 113: Not supported
  5. 114 - 116: Not supported

Edge

  1. 12 - 112: Not supported
  2. 113: Not supported

Safari

  1. 3.1 - 6.1: Not supported
  2. 7 - 7.1: Not supported
  3. 8 - 16.4: Not supported
  4. 16.5: Not supported
  5. 16.6 - TP: Not supported

Firefox

  1. 2 - 112: Not supported
  2. 113: Not supported
  3. 114 - 115: Not supported

Opera

  1. 9 - 98: Not supported
  2. 99: Not supported

IE

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

Chrome for Android

  1. 113: Not supported

Safari on iOS

  1. 3.2 - 6.1: Not supported
  2. 7: Not supported
  3. 8 - 16.4: Not supported
  4. 16.5: Not supported

Samsung Internet

  1. 4 - 20: Not supported
  2. 21: Not supported

Opera Mini

  1. all: Not supported

Opera Mobile

  1. 10 - 12.1: Not supported
  2. 73: Not supported

UC Browser for Android

  1. 13.4: Not supported

Android Browser

  1. 2.1 - 4.4.4: Not supported
  2. 113: Not supported

Firefox for Android

  1. 113: Not supported

QQ Browser

  1. 13.1: Not supported

Baidu Browser

  1. 13.18: Not supported

KaiOS Browser

  1. 2.5: Not supported
  2. 3: Not supported

Chrome 20-26 had partial support behind a flag, though this was later removed.

Resources:
Bug on Firefox support: wontfix
Experimental polyfill
Article