User Authentication: Best Practices for Secure Login Systems
User authentication is the first line of defense against unauthorized access—but it’s also one of the easiest things to get wrong. Too many applications either sacrifice security for convenience or frustrate users with unnecessary complexity.
For companies building SaaS applications, managing authentication at scale is a challenge. That’s why many teams turn to authentication-as-a-service solutions like Supabase, Firebase, and Clerk. But even with these tools, developers still face integration hurdles, security concerns, and user experience trade-offs.
This guide will break down best practices for secure user authentication, explore common mistakes developers make, and introduce a simpler way to handle authentication without reinventing the wheel.
What Is User Authentication?
User authentication is the process of verifying a user's identity before granting access to an application. The best authentication systems balance security and user experience—keeping attackers out while ensuring legitimate users can sign in easily.
How Does Secure User Authentication Work?
A typical secure login system follows this sequence:
- User enters credentials (e.g., email + password or biometric data).
- The server verifies the identity against stored credentials.
- If authentication is successful, the server creates a session and issues an authentication token.
- The token is used to authenticate subsequent user requests.
A good authentication system minimizes risk at every step while maintaining frictionless user access.
Best Practices for Secure User Authentication
To build a secure, user-friendly authentication system, follow these best practices:
1. Avoid Storing Plaintext Passwords
Passwords should never be stored in plaintext. Instead:
- Hash passwords using bcrypt, Argon2, or scrypt.
- Use a slow hashing function to prevent brute-force attacks.
- Implement password rotation and compromised credential checks.
Many modern authentication services handle password security for you—offloading the burden of encryption, hashing, and credential management.
2. Implement Multi-Factor Authentication (MFA)
MFA adds an extra layer of security by requiring users to verify their identity using a second factor, such as:
- TOTP-based authentication (Google Authenticator, Authy)
- WebAuthn (Yubikeys, Face ID, Windows Hello)
- Magic links (email-based login without passwords)
75% of cloud security breaches involve weak or stolen passwords. MFA significantly reduces this risk.
3. Use Secure Token Management
How should authentication tokens be stored?
One of the most common security mistakes is storing authentication tokens in local storage, which exposes them to XSS attacks.
Best practices for token storage:
- Use HttpOnly, Secure Cookies instead of local storage.
- If using JWTs (JSON Web Tokens), set short expiration times and require refresh tokens.
- Rotate session identifiers after login to prevent session fixation attacks.
4. Secure Session Management
How do you prevent unauthorized access once a user logs in?
- Short-lived session tokens reduce exposure in case of compromise.
- Implement logout endpoints that invalidate sessions immediately.
- Use rate-limiting to prevent brute-force attacks on login endpoints.
Many modern authentication solutions (e.g., Supabase, Firebase, Clerk) handle session management for you—but knowing how it works under the hood is essential for security.
Choosing the Right Authentication Approach
Should You Build or Buy Your Authentication System?
If your team is spending weeks or months implementing authentication, it’s worth asking:
Would it be easier to integrate an authentication service instead?
The case for using authentication-as-a-service:
- Time savings: Offload session management, password hashing, and OAuth integration.
- Security: Providers like Supabase and Firebase handle compliance, encryption, and token security for you.
- Scalability: A hosted solution ensures multi-tenancy, user roles, and SSO support without extra dev work.
What If You Don't Want to Manage Supabase or Firebase?
Many developers turn to tools like Supabase, Firebase, or Clerk because they don’t want to build authentication from scratch. But even these solutions require setup, maintenance, and ongoing security updates.
For teams who want authentication without the overhead, Update provides an alternative—handling secure user authentication without the need for third-party databases or custom authentication workflows.
If you just need authentication, Update simplifies user sign-ups, logins, and session management.
If you need authentication + billing, Update connects identity management with payments seamlessly.
No more stitching together multiple services or worrying about token security, session expiration, or scaling authentication—it’s handled for you.
Final Thoughts: The Future of User Authentication
Authentication isn’t just about logging in. It’s about trust, security, and user experience.
The best systems are:
- Invisible when they work
- Unforgiving when attacked
- Built with failure in mind
Want to simplify authentication for your SaaS app? Explore how Update makes authentication effortless—without the headaches.