Build a login system with AI
Use AI to ship a secure login from scratch: sign-up, sign-in, sign-out, who-can-see-what, and the security traps beginners hit.
In one sentence
A login system is authentication (who you are) plus authorization (what you may do). Spell out the security rules so the AI doesn't hand you holes.
What you'll build
A working prototype that can register, sign in, sign out, and gate access by role — and you know which security rules you must not skip.
First: login is really two things
Most people think "login" is just typing a username and password. It's actually two jobs: authentication (who you are) and authorization (what you may do). Once you're authenticated, the system hands you an invisible "pass" that you carry on every request, so it knows it's you — and whether you're allowed to do that action.
This guide isn't about memorizing syntax. It's about how to describe the requirement to the AI so the login it builds is secure, not just something that looks like it works but gets bypassed on day one.
Three paths: build it, use a platform, or use social login
| Approach | Good for | Watch out for |
|---|---|---|
| Build password login yourself | Full control, learning the internals | You own hashing, token expiry, brute-force defense |
| Use an Auth platform | Fast and secure | Vendor lock-in; most have a free tier |
| Social login (Google, etc.) | Lowering the sign-up barrier | You still create a session on your side |
For beginners the pragmatic choice is usually "platform Auth + social login": hand the riskiest part (storing passwords) to specialists and focus your energy on "who can see what."
Tell the AI this, or it will give you holes
AI is great at writing login that runs — but the defaults aren't always safe. When you prompt it, demand these explicitly:
- Passwords must be hashed (bcrypt or argon2) and never stored in plain text.
- Tokens/sessions issued at login must expire and be revocable (invalidated on logout or password change).
- Put the token in an httpOnly cookie, not anywhere front-end JavaScript can read.
- Permission checks happen on the backend. The front end only hides buttons — that is never a security boundary.
Paste that list to the AI as your "acceptance criteria," then have it implement step by step.
Architecture
Traps beginners fall into
- Storing passwords in plain text: one leak exposes everyone's password. Always hash.
- Tokens with no expiry: stolen once, used forever. Short expiry + revocable.
- Letting the front end decide permissions: putting the "is admin?" check in the UI means anyone can tweak it and walk in.
- Secrets in the front end: an API key or signing secret that reaches the browser is effectively public.
Next steps
- Shore up the concept first: Authentication
- Then plan what user data to store: Design a database with AI
Frequently asked questions
Why not just have the AI build login for me — why learn any of this?
AI is great at login that *runs*, but the defaults aren’t always safe: plain-text passwords, tokens with no expiry, permission checks in the front end. You don’t need to write it, but you do need to recognize these rules so you can demand them as acceptance criteria and check the AI actually met them.
Is rolling my own password login safer, or using Google login?
For beginners, social login (Google, etc.) or an Auth platform is usually safer, because the easiest part to get wrong — storing passwords — is handed to specialists. Rolling your own is fine, but you own hashing, brute-force defense and token management, which is a higher bar.
References
- Authentication Cheat Sheet — OWASP
- Session Management Cheat Sheet — OWASP
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