Most of the features these programs have translate fine; you won't have a good experience unless you're using their client or another client with a similar feature set (though things to tend to degrade gracefully), but that's fine for the most part. It still gives you a nice realtime API for developing other stuff on top of it, most people will use your clients anyways, and if you're on a feature phone or something and can't use the first-party clients, you can still connect. It's a win-win.

> Chat programs have a lot of proprietary features that won't translate through XMPP.

Most chat networks are still built around xmpp - they’re just not federated and likely using private extensions.

Pretty sure XMPP included extensions for sending arbitrary HTML and binary attachments. Now, support for janky mobile connections, that's another matter.

XMPPs actually been really good at this for quite some time; despite XML being a bit verbose, it compresses very well and it's had TCP like stream management at the application protocol layer for ages, among other things. It was pretty bad at low-bandwidth connections in the early 2000s, but now there are people running it over extremely low bandwidth high frequency radio, so a janky phone connection is no problem.

XMPP had extensions just for that crap. The trick was getting clients that all supported them.

That's exactly my point. Thank you for making it for me.