Securing Your APIs: A Deep Dive into OAuth2 and JWT Best Practices

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Meerako — Dallas, TX experts in building secure, enterprise-grade APIs and authentication systems.

Introduction

In modern web development, your API is everything. It's how your frontend (React/Next.js), your mobile app, and potentially third-party partners interact with your data and business logic. An unsecured API is not just a bug; it's an open invitation for a catastrophic data breach.

Two technologies form the bedrock of modern API security: OAuth2 (for authorization) and JWT (JSON Web Tokens) (for authentication). We introduced these in our Authentication Guide, but understanding how they work together and the best practices for implementing them is critical.

As a 5.0★ company building secure software, Meerako implements these standards rigorously. This guide is a deeper dive for developers and architects.

What You'll Learn

• Recap: Authentication vs. Authorization.
• The OAuth2 Authorization Code Flow (the standard for web apps).
• How JWTs fit into the OAuth2 flow (ID Tokens vs. Access Tokens).
• Best practices for secure JWT handling (storage, expiration, signing).
• Why using a managed service (like AWS Cognito) is the Meerako way.

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Recap: Authentication vs. Authorization

• Authentication (AuthN): Who are you? (Proving your identity, e.g., logging in with a password or Google).
• Authorization (AuthZ): What are you allowed to do? (Checking your permissions, e.g., Are you an admin? Can you view this document?).

JWT is primarily used for Authentication. OAuth2 is primarily used for Authorization (delegating access).

The OAuth2 Authorization Code Flow (The Standard)

This is the most common and secure OAuth2 flow for web applications (e.g., when your app asks a user to "Log in with Google").

1. User Clicks "Log in with Google": Your app redirects the user to Google's login page (the Authorization Server) with specific parameters (client_id, redirect_uri, scope, response_type=code).
2. User Logs In & Consents: The user logs into Google and approves your app's request (e.g., "Allow MeerakoApp to access your email address").
3. Google Redirects Back with a Code: Google redirects the user back to your specified redirect_uri with a short-lived, one-time-use Authorization Code in the URL.
4. Your Backend Exchanges Code for Tokens: Your backend server securely sends this code (along with your app's client_secret) directly to Google's token endpoint.
5. Google Returns Tokens: If the code is valid, Google returns Access Token and (usually) an ID Token.

ID Tokens vs. Access Tokens (JWTs in OAuth2)

This is where JWTs come in.

• ID Token (JWT): This token proves who the user is (Authentication). It's a JWT containing claims about the user (e.g., sub (subject/user ID), name, email). Your application verifies the signature of this token to confirm the user's identity and can use the claims to create a local session or user profile.
• Access Token (Usually Opaque, Sometimes JWT): This token represents the permission your app has to access resources on behalf of the user (Authorization). It's sent in the Authorization: Bearer <access_token> header when your app calls Google's APIs (e.g., Google Calendar API). The format isn't strictly defined; it might be a JWT or just a random string.

Key Takeaway: Your app uses the ID Token to log the user into your app, and the Access Token to call external APIs (like Google's) on their behalf.

JWT Best Practices for Your API

When securing your own backend API (not interacting with Google), you'll typically issue your own JWTs after a user logs in via password or social login.

1. Use Strong Signing Algorithms: Use RS256 (Asymmetric - requires public/private keys) or HS256 (Symmetric - requires a shared secret). Never use alg: none.
2. Keep Payloads Small: Only include essential claims (like userId, role). Don't stuff large amounts of data into the JWT.
3. Set Short Expiration Times (TTL): Access Tokens should be short-lived (e.g., 15 minutes to 1 hour). Use Refresh Tokens (long-lived, securely stored tokens) to get new Access Tokens without forcing the user to log in again.
4. Store Tokens Securely:
   • Web: Store JWTs in httpOnly cookies. This prevents JavaScript (and XSS attacks) from stealing the token.
   • Mobile: Store tokens securely in the device's keychain/keystore.
   • Never store tokens in localStorage!
5. Validate on Every Request: Your API must validate the JWT's signature, expiration, and claims on every single incoming request using middleware.

Why Meerako Uses Managed Auth (AWS Cognito)

Implementing all of this correctly—OAuth2 flows, secure JWT handling, refresh tokens, MFA, password hashing—is complex and error-prone.

This is why Meerako recommends managed Identity Providers (IDaaS) like AWS Cognito or Auth0.

These platforms:

• Implement OAuth2 and OIDC (OpenID Connect - the layer on top of OAuth2 that provides the ID Token) correctly and securely.
• Handle secure user management, password hashing, MFA, etc.
• Issue standards-compliant JWTs that your backend can easily validate.

By leveraging these services, we provide our Dallas clients with enterprise-grade security without reinventing the wheel.

Conclusion

OAuth2 and JWT are the cornerstones of modern API security. OAuth2 provides the framework for delegated authorization (like social logins), while JWTs provide a secure, stateless way to handle authentication for your own API.

Understanding the flows and best practices is crucial, but for most applications, leveraging a managed IDaaS provider is the most secure and efficient path to implementing robust authentication and authorization.

Need to build a secure, scalable API with enterprise-grade authentication?

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🧠 Meerako — Your Trusted Dallas Technology Partner.

From concept to scale, we deliver world-class SaaS, web, and AI solutions.

📞 Call us at +1 469-336-9968 or 💌 email [email protected] for a free consultation.

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