What is Authentication?
The process of verifying that a user is who they claim to be. It answers the question 'Who are you?' before granting access to a system.
In plain English
Authentication is like showing your ID at the door of a nightclub. The bouncer checks your photo matches your face before letting you in. Without this check, anyone could walk in claiming to be someone else.
How it works
Authentication typically involves a user providing credentials — such as a username and password, a social login token, or a biometric scan — which the system then verifies against stored records. Modern apps often use token-based authentication where, after initial login, the server issues a signed token (like a JWT) that the client sends with each subsequent request. This avoids re-checking the password on every API call.
Why it matters for AI-built apps
AI coding tools can scaffold login flows quickly, but often generate insecure defaults — storing passwords in plain text, using weak token expiration settings, or skipping email verification. A single authentication flaw can expose every user account in your app. Getting auth right from the start is far cheaper than fixing a breach later.
Common issues
Passwords stored without hashing, tokens that never expire, missing rate limiting on login endpoints, no account lockout after failed attempts, and session tokens sent over unencrypted connections. AI-generated code frequently omits CSRF protection on login forms and may hardcode secret keys used for token signing.
Best practices
Use a battle-tested auth library or service (like NextAuth, Supabase Auth, or Auth0) rather than rolling your own. Always hash passwords with bcrypt or argon2. Enforce strong password policies. Implement multi-factor authentication. Set short token expiration times and use refresh tokens. Log all authentication events for auditing.
Frequently asked questions
My AI tool generated a login system — is it secure?
Probably not out of the box. AI-generated auth code often lacks password hashing, rate limiting, and proper token management. Have it reviewed by a security-focused engineer or use a managed auth provider like Supabase Auth or Auth0 to reduce risk.
What's the difference between authentication and authorization?
Authentication verifies WHO you are (login). Authorization determines WHAT you're allowed to do once logged in (permissions). You need both — authenticating a user means nothing if every authenticated user can access admin features.
Should I build my own auth or use a third-party service?
For almost every startup, use a third-party service. Auth is deceptively complex, and mistakes lead to data breaches. Services like Supabase Auth, Clerk, or Auth0 handle the hard parts — password hashing, token rotation, MFA — so you can focus on your product.
Check your app
Get a professional review of your app at a fixed price.
Security Scan
Black-box review of your public-facing app. No code access needed.
- OWASP Top 10 checks
- SSL/TLS analysis
- Security headers
- Expert review within 24h
Code Audit
In-depth review of your source code for security, quality, and best practices.
- Security vulnerabilities
- Code quality review
- Dependency audit
- AI pattern analysis
Complete Bundle
Both scans in one package with cross-referenced findings.
- Everything in both products
- Cross-referenced findings
- Unified action plan
100% credited toward any paid service. Start with an audit, then let us fix what we find.
Worried about authentication in your app?
Get a professional code audit ($19) or book a free call to discuss your concerns.