Why I Ditched the Library
For years, I used Auth0, Firebase Auth, and Passport.js without thinking twice. They handled the hard stuff — token management, security patches, OAuth flows. Why reinvent the wheel?
Then I joined a startup with a tight budget and a weird requirement: we needed custom auth logic that didn’t fit any library’s box. That’s when I decided to build our own.
What I Learned Building Auth From Scratch
First, I want to be clear: I’m not saying libraries are bad. Most teams should use them. But building our own taught me things I never would have learned otherwise.
1. You start caring about security details
When you’re responsible for storing passwords, you suddenly care about bcrypt rounds, salt length, and timing attacks. I read OWASP guidelines I would have skipped otherwise.
2. You understand token flow deeply
Libraries abstract away JWT structure, expiration logic, and refresh token rotation. Building it myself meant I knew exactly what every line did.
3. Debugging gets faster
When something breaks in auth, you can’t just blame the library anymore. You have to own it. That forced me to understand every edge case.
The Trade-offs I Didn’t Expect
- Time cost: It took 3 weeks to build what a library gives you in 10 minutes
- Maintenance burden: I now have to manually update security patches
- Feature gap: Social login, MFA, and account recovery took extra work
What I’d Do Differently
If I were starting over today, I’d probably use a library but wrap it in my own abstraction layer. That way I get security benefits without tight coupling. The middle path is usually the smart one.
The Bottom Line
Building your own auth is worth trying at least once. You’ll learn more about security in a month than years of using libraries. But for production apps with real users? Respect the experts. Use the library, but understand what it’s doing.