[JimDabell]

> When I think they meant to say support for most users isn't there until next year.

They did say that though:

> full, reliable support

“Reliable” in the context of browser support means widely supported in the browser versions people actually use – i.e. web developers can rely upon it being there. Something that is only available in a browser version released last week is not “reliable” in the sense of browser support.

[poincaredisk]

But Firefox supports it. Firefox developers can't do anything else to improve the support. There's no reason to suspect this feature is not implemented in a reliable way.

The onus is now on users that use Firefox. You're right that many Firefox users don't run the newest version, and you can't in general rely on a Firefox user having a browser new enough to support this feature.

Maybe this is a pedantic distinction, but it feels weird to say "Firefox doesn't support X" to mean "Old version of firefox, that some people use, doesn't support X"

[JimDabell]

> There's no reason to suspect this feature is not implemented in a reliable way.

As I said in my earlier reply, that is not what “reliable” is referring to in the context of browser support. “Reliable” means “We can rely upon our users having it available in their browser”.

This feature does not have reliable support and will not have reliable support until common browser support matrices – of which Firefox ESR is a part – includes support.

OP was correct to say that browser support is unreliable and that Firefox ESR is the thing causing this and will continue to be until next year.

Are you a web developer? “Reliable browser support” is a very well-understood term of art.