I’ve never heard of them before, but it seems that support is very spotty at best, and probably not something to rely on. To add some links:
- caniuse.com (raw data); the referenced section on MDN no longer exists
- Google developer docs
- MDN mentions:
- old YouTube announcement (2008), may have been the originator of the working group
- Working Group page (closed in 2013 after releasing the latest draft)
- scroll-to-text-fragment drew inspiration from media fragments
- Chromium (Blink) tests for media fragments. The parser code hasn’t been touched in years, apart from some general fixes.
- window.location.fragmentDirective might be something to keep an eye on. If MF get a revival or extended support, it might happen there (disclaimer: this is my uninformed guess).