Building your own signup, login, and password reset flow, or reaching for a dedicated auth provider like Supabase Auth, Clerk, or Auth0, is a decision that gets made quickly and rarely revisited. Both are legitimate choices. They come with genuinely different risk profiles worth understanding before you pick one, not after.
What building it yourself actually involves
Rolling your own auth means correctly handling password hashing, session management, token expiration and rotation, password reset security, rate limiting, and account enumeration prevention, among other things, all of which I've written about individually on this blog as their own potential mistakes. None of these are impossible to get right. Together, they're a meaningful surface area of well-documented, specific ways to get something subtly wrong, each with real consequences if missed.
What a dedicated auth provider actually buys you
A mature auth provider has usually already solved each of those specific problems, correctly, at scale, across a huge number of other applications, and has a dedicated team whose full-time job is keeping that solution correct as new attack patterns emerge. Using one means inheriting that ongoing work rather than reinventing and re-verifying it yourself, for a part of your app where a subtle mistake has outsized consequences.
Why this isn't automatically the obvious choice for everyone
A dedicated provider adds a dependency, sometimes a cost, and a certain amount of integration work to fit your specific app's needs. For an extremely simple internal tool with a handful of known users, the tradeoff might reasonably favor something simpler. For anything with real, growing user data, an argument the other way, that using a provider is worth the cost, gets stronger the more your app actually has to lose.
What matters most if you do build it yourself
- Never write your own password hashing algorithm. Use an established, well-vetted library for this specifically, even if you build everything else yourself.
- Test every one of the specific failure modes I've written about individually: token expiration, session invalidation on password change, rate limiting, account enumeration through the reset flow.
- Get an outside review of the auth system specifically, given how much rides on it being correct, even if you skip a full review of everything else.
- Revisit the decision periodically. What was reasonable to build yourself at a small scale can become a genuinely worse tradeoff once real user volume and real stakes grow around it.
This isn't really a question with one right answer for every app. It's a question worth actually asking on purpose, weighing what you gain in control and simplicity against what a specialized provider has already solved, rather than defaulting to whichever felt fastest to wire up on the day you first needed a login screen.