User login can make a web app personal, but it also introduces responsibility. Authentication answers who is signed in; authorization answers what that person is allowed to do. A reliable app needs both.
Choose a trusted authentication service
Prefer a maintained provider or framework rather than inventing password storage. Follow its current setup instructions and configure the production domain and redirect URLs.
Build the complete account journey
Test registration, email verification if enabled, login, logout, password reset, and expired sessions. Give users helpful messages without exposing unnecessary account information.
Protect private pages and data
Redirect signed-out users away from private screens, but do not rely on redirects alone. Every backend operation that reads or changes private records must check permissions too.
Test more than one account
Create two test users and attempt to access each other’s records. Try direct URLs and API requests, not just visible navigation. Changing an identifier should not grant access.
Before release
- Sign-up and sign-in work on the live domain.
- Password recovery works end to end.
- Private routes and backend data are protected.
- Two-account permission tests pass.
- Secrets and session tokens are handled safely.
Login is not finished when the form looks right. It is finished when account flows work reliably and each user can access only what they should.