I've been looking at several authentication providers: - Supabase Auth - Zitadel - Supertokens - Ory
Self-hosted vs Cloud based: I would like to select something that I can self-host (or run locally on docker for development). However, some years ahead, I might move to the cloud (depends on the revenue).
Does anyone have experience with the above mentioned services? If yes, could you please provide your experiences with it.
Or if there's any better service that I missed looking into?
There is no problem moving a self-hosted auth system into the cloud as you can move it there the same way you move the rest of your application.
Circa 2001 I built a "user management" library in PHP which was inspired by this
https://philip.greenspun.com/doc/index
that depended on an "auth module" that was maybe 50-100 lines of code in most programming languages so there were some screens for logging in, email verification, changing your passwords, etc. and also an administrative interface and system for sending both transactional emails and marketing blasts, it all worked pretty well for 350,000+ users. The rest of the application could be written in Perl, Java, ColdFusion, ASP, WiTango or any other system that supports cookies and mysql database access. The vision was that one could build a "portal" by modifying best-of-breed blog, forum, and other software to use my auth module.
I used it for quite a few sites but never got any uptake on the open source project, I think people just didn't agree with the vision.
I didn't see anything similar come along until 2013 a bunch of "me too" companies came out with user management systems that worked as a SaaS which struck me as absolutely insane because of what I said the in the first paragraph but these had a huge amount of uptake for reasons that baffle me completely. I guess some people don't find business interesting enough unless it has an element of Russian Roulette.
That being said with ZITADEL you can also move between self-hosted and cloud: https://zitadel.com/docs/guides/migrate/sources/zitadel
ps: I'm biased (see bio).