7 Things You Must Know Before Building a Login & Registration System

Think about your favorite app or website. What’s the very first thing it asks you to do? Sign up or log in. That simple little form you fill in—your email, your password, maybe your username— that’s what we call a login and registration system.

Now, don’t let the simplicity fool you. Behind that form hides one of the most important pillars of any digital product: security and trust. If you get it right, users will feel safe, confident, and ready to stick around. If you get it wrong… let’s just say it could be game over for your project.

So let’s break it down in plain English: here are the 7 things you absolutely need to know before building your own login system.

1. It All Starts With the Password

A login system is basically a digital door—and the password is the key. But here’s the catch: if you keep a copy of everyone’s keys in a drawer (aka storing passwords in plain text), you’re setting yourself up for disaster.

Instead, the golden rule is: never store passwords directly. Ever. Even the database administrator should never be able to see a user’s password.

2. Hashing: The One-Way Street of Security

So, how do we protect passwords? By using something called hashing.

Imagine throwing your password into a special blender. Out comes a unique “hash” value that looks nothing like the original. Here’s the genius part:

  • You can go forward (password → hash).
  • But you can’t go backward (hash → password).

That means even if hackers get access to your database, all they’ll see is a bunch of random gibberish.

To make it even harder for attackers, developers add a salt (a random string mixed into the password before hashing). This makes sure that even if two users pick the same password, their hashes will look completely different.

3. Don’t Reinvent the Wheel (Use Trusted Libraries)

Good news: you don’t need to invent your own hashing system. That would be like trying to build your own lock instead of buying one from a trusted brand.

Some of the most reliable options today are:

  • Bcrypt – A battle-tested library that balances security and performance, and has been around for decades.
  • Argon2 – A modern algorithm, winner of the Password Hashing Competition, designed to resist even the most advanced attacks.
  • PBKDF2 – A well-established choice, often built into frameworks and widely recommended for enterprise-level applications.

These libraries handle the heavy lifting of hashing and salting, so you can focus on building the fun parts of your product instead of worrying about cryptography.

4. Think Twice About What Data You Collect

Sure, you’ll need an email and a password. But before you start asking for phone numbers, birthdays, or favorite colors, stop and ask yourself: Do I really need this information?

Every piece of personal data you collect comes with responsibility. Not just technical responsibility (keeping it secure), but often legal responsibility (depending on privacy laws like GDPR).

Less is more. If you don’t absolutely need it, don’t ask for it.

5. Third-Party Authentication: The Smart Shortcut

Here’s a secret: most startups and even big companies don’t build their login systems completely from scratch anymore. Why? Because authentication is hard—really hard.

That’s why third-party solutions like Google Sign-In, Facebook Login, or services such as Firebase Authentication exist. They provide:

  • Bulletproof infrastructure
  • Up-to-date security practices
  • Easy integration and even free plans (like Firebase’s Spark plan)

If you want to focus on growing your business instead of constantly worrying about security patches, this is a no-brainer.

6. Don’t Forget the “Small” Features (They’re Not So Small)

A good login system is more than just “email + password”. Users today expect:

  • Password reset options (because, yes, people forget all the time)
  • Email verification (to avoid fake accounts and spammers)
  • CAPTCHAs to stop bots from flooding your site
  • Even a simple honeypot field—a hidden input that bots will accidentally fill, instantly revealing themselves

These small details massively improve both security and user experience.

7. The Extra Layer: Multi-Factor Authentication (MFA)

Want to take your security to the next level? Add multi-factor authentication (MFA). This means users need not just a password, but also a second step—like a code sent to their phone or email.

It might feel like overkill at first, but MFA is becoming the standard for any serious app. And the best part? Many third-party providers like Firebase make it easy to add.

Final Thoughts: Your Login System Is Your Reputation

At the end of the day, your login and registration system isn’t just about letting users in. It’s about earning their trust. When users know their data is safe, they’ll feel confident investing their time, attention, and even money into your platform.

My final tip: start simple but secure. Use proven libraries, lean on third-party services when possible, and never compromise on password security. As your project grows, you can layer on advanced features like MFA.

Because in the world of digital products, trust isn’t just important—it’s everything.