Oh man, we're almost home now.
SDL3 is officially ABI-locked, which is to say we might add interfaces, but the ones that are there now will not be changed or removed. Which is also to say: you can now safely use it in your games without us pulling the rug out from under you.
If you're migrating from SDL2, we have a comprehensive migration guide over here, which lists literally every single API change, organized by subsystem. There's even a coccinelle script to automate the busywork parts of the migration.
If you want to get the power of SDL3 but aren't quite ready to leave SDL2, we have been building sdl2-compat from the start this time, so you can drop a binary-compatible SDL2 library into your game that uses SDL3 for all the heavy lifting. That works right now. You can even chain and SDL-1.2 program through sdl12-compat to sdl2-compat, to make it a real SDL3 app!
But I've got to say: you might look at our New Features page and break up with SDL2 immediately.
We also have a lot of documentation. The forever-complaint about SDL2 is that the documentation was bad, so we worked on that. If you were to ride your time machine to a Waldenbooks in the 1990s and peruse their computer section--it's a sadness if you never knew the joy of this sort of perusal--then the SDL3 book would be over 2000 pages long. You'd need to attach a trailer to your time machine to bring it home. Or just download the PDF. This documentation is automatically shared between the wiki and the headers as changes are made, and can be used to generate manpages, too. And, of course, if you love HTML but hate TCP/IP, you can download the wiki as static pages for offline perusal.
The official announcement is over here. This is technically not the official first SDL3 release, as we intend to smash through a bunch of bugs before we ship an official SDL 3.2.0 (which sounds like not a first release, but it guarantees we can see clearly when prerelease versions are in use).
If you move your project to SDL3, I'd love to hear from you! Let me know how the migration went and what you liked (and also, what you hated).
In the meantime, we have more fun stuff coming...we're not just fixing bugs, we're still adding more cool stuff to SDL3, so stay tuned!