JWT Authorization: How It Works and Implementing in Your Application

JSON Web Token (JWT) is a commonly used user authentication and authorization standard, used to exchange data in a secure manner. Made up of three components, a header, a payload, and a signature, it’s becoming more and more commonly used. Read on to discover the best use cases for JWT authorization, learn how it works, and access best practices that can help you implement it effectively in your organization.

What Is JWT Authorization?

JWT authorization is a stateless way to control what an authenticated user can do, using a JSON Web Token — a compact, URL-safe, digitally signed structure carrying claims (statements about that user) from client to server. Because those claims travel inside the token, the server verifies what a request may do by checking the signature alone, with no session lookup required.

For more background, see our article on JWT authentication.

In this article:

How Does JWT Authorization Work? 

JWT authorization works in five steps: the server authenticates the user and issues a signed JWT containing their claims; the client stores that token and attaches it to the Authorization header of every subsequent request; the server verifies the token’s signature and reads the claims to decide what the request is allowed to do. No database session lookup happens at verification — the token itself is the credential.

• Authentication: The client sends the user’s credentials to the server, which authenticates the user and generates a JWT containing information about the user.
• Issuing the Token: The server sends the JWT back to the client, which stores it for future use.
• Sending the Token: When the client wants to access a protected resource on the server, it sends the JWT in the Authorization header of the HTTP request.
• Verifying the Token: The server receives the request and verifies the JWT by checking its signature using the secret key that was used to sign it. If the JWT is valid, the server extracts the information contained in it and uses it to determine what actions the user is authorized to perform.
• Authorizing the Request: If the user is authorized to access the resource, the server returns the requested data. If the user is not authorized, the server returns an error message.

JWT authorization enables secure and efficient communication between the client and server, as the server does not need to store any session information to keep track of the user’s authentication status. This makes it ideal for use in microservice architectures and other decentralized systems, where multiple independent components need to communicate with each other in a secure manner.

Related content: Read our guide to asp net authorization

Authentication Claims vs. Authorization Claims in a JWT

A JWT typically carries two different kinds of claims that solve two different problems: authentication claims identify who is making the request — a user ID, email, or session ID — while authorization claims state what that identity is allowed to do, usually as roles or permission keys. A valid signature only proves who the caller is, not what they’re currently permitted to do.

Most JWT explainers stop at “a JWT can carry roles” without separating these two categories, but the distinction matters in practice. OIDC’s ID token, for example, standardizes the identity side of this — see our guide to OpenID Connect (OIDC) for how authentication claims like sub and email get their own standard. Authorization claims have no equivalent standard; each platform defines its own. Frontegg’s own JWTs, for instance, put identity claims (sub, email, name) alongside a separate roles and permissions claim set that its backend SDKs check to perform role-based access control — missing or stale permission claims will cause those authorization checks to fail. The practical implication for anyone designing their own token: decide up front which claims answer “who” and which answer “what can they do,” because they get validated, cached, and revoked differently. For a deeper look at structuring the “what can they do” side specifically — not just as JWT claims but as a role/permission model — see user role and permission management.

The limitation: authorization claims are static until the token is reissued

JWTs are well-suited to coarse-grained authorization — checking whether a caller holds a given role or permission key — but they weren’t designed for fine-grained, frequently-changing permission checks, because a signed JWT’s claims can’t be edited in place. Once issued, a JWT’s authorization claims stay exactly as they were at issuance until that token expires or is reissued, even if the user’s actual permissions change in the meantime.

This isn’t a hypothetical: if an administrator downgrades a user’s role mid-session, a JWT that already has that user’s old, broader permission claims baked in has no way to “know” about the change until it’s reissued. The standard mitigation is short token lifetimes plus background refresh, not longer-lived tokens with more claims crammed in. It’s also why Frontegg’s own documentation recommends configuring JWT expiration to a maximum of a few minutes and refreshing access tokens automatically in the background before they expire, rather than issuing long-lived tokens and hoping permissions don’t change in the interim. JWTs also don’t scale well to very fine-grained models like per-resource or attribute-based access control — once a token needs to represent “this user can edit these 40 specific records,” it’s usually a sign the authorization decision belongs in a server-side check against current data, not in the token.

API Keys vs. JWT Authorization 

API keys and JWTs solve different problems: an API key is an opaque string that identifies which client is calling and can gate how much access that client gets, while a JWT carries the caller’s actual identity and permission claims inside a signed, self-contained token. API keys are simpler to issue and revoke; JWTs carry richer, verifiable information but inherit the static-claims limitation described above.

What are API keys?

API keys usually consist of a long string of characters, which are sent along with the API request as a parameter or in headers. An API key is typically generated by an API provider and is shared with a client, who needs to include it with every API request. API keys can be used to identify the client and limit the usage of the API.

What are the differences?

JWT authorization uses a JWT to represent the user’s identity and access rights. The JWT is usually generated by the authentication server after the user logs in and contains the user’s identity and access rights. The JWT is then sent with every API request as a bearer token in the authorization header.

Here is a comparison table between API keys and JWT authorization:

In summary, while API Keys are simpler to use, they are less secure and less flexible than JWT authorization. JWT Authorization provides a more secure and flexible mechanism for authenticating and authorizing access to an API.

General Steps for Implementing JWT Authorization in Your Application

Implementing JWT authorization takes five steps: stand up a server-side app that can issue and verify tokens, install a JWT library for your stack (such as Node.js’s jsonwebtoken), authenticate the user through your existing login flow, sign a JWT containing their identity and role/permission claims, and verify that signature — and the claims it carries — on every subsequent request before authorizing an action.

1. Set up a server-side application: You’ll need a backend application that will generate and verify JWTs. You can use any server-side language and framework, such as Node.js and Express.
2. Install the necessary packages: You’ll need to install a JWT library for your server-side language. For example, if you’re using Node.js, you can install the jsonwebtoken library.
3. Implement authentication: Your server-side application will need to implement authentication to verify the user’s credentials. You can use methods like email/password authentication or social media authentication.
4. Generate the JWT: Once the user has been authenticated, your server-side application will generate a JWT that contains information about the user, such as the user’s ID, name, and roles. You can sign the JWT using a secret key or a public/private key pair.
5. Send the JWT to the client: The server will send the JWT to the client, which will store it for future use.
6. Send the JWT with every request: When the client wants to access a protected resource on the server, it will send the JWT in the Authorization header of the HTTP request.
7. Verify the JWT on the server: The server will receive the request and verify the JWT by checking its signature using the secret key that was used to sign it. If the JWT is valid, the server will extract the information contained in it and use it to determine what actions the user is authorized to perform.
8. Authorize the request: If the user is authorized to access the resource, the server will return the requested data. If the user is not authorized, the server will return an error message.

With these steps, you can implement JWT authorization in your application and secure the communication between the client and server.

References

• JSON Web Token (JWT) — RFC 7519
• JWTs — Use Responsibly (Permit.io)

Authentication and Authorization with Frontegg

The industry standard today is to use Authentication providers to “build the door”, but what about Authorization (the door knob)? Most authentication vendors don’t go the extra mile, forcing SaaS vendors to invest in expensive in-house development. This often delays core technology development and impacts developer productivity, something that negatively impacts innovation and time-to-market (TTM) metrics. 

Frontegg’s end-to-end user management platform allows you to authenticate and authorize users with just a few clicks. Integration takes just a few minutes, thanks to its plug-and-play nature. It’s also multi-tenant by design. 

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