However, this approach can be inconvenient for users because it would cause their tokens to expire without reason, logging everyone out.Īnother suggestion is to keep a list of invalidated tokens in the database. One proposed solution is to change the server secret key, which would invalidate all JWTs. This issue is significant - for instance, when dealing with bad actors, suspending their account won’t immediately revoke their access because JWTs persist until expiration. This is because they are self-contained and do not have a central authority for invalidation, unlike traditional sessions. Invalidating a single token in JWT can also be a challenge. This is as bad as it sounds: an XSS attack could give an external attacker access to the token. For a little context, If you store it inside localStorage, the data accessible by any script inside your page. Storing sensitive data in localStorage comes with many problems on its own. This often leads people to store the JWTs in localStorage instead. When used with cookies, this either adds up to a lot of overhead per request or exceeds the allowed storage space for cookies, which is 4KB. In many complex real-world apps, you may need to store a ton of different information. Here’s a non-exhaustive list of problems associated with using JWT as a session mechanism. These might seem like valid reasons, but there are quite a few downsides to using JWT as a session mechanism. Using JWTs for session tokens might seem like a good idea at first because it is cryptographically signed and stores user details, thus eliminating database lookup. The inefficiencies of JWT for user sessions The user’s identity and authorization details are extracted from the token, eliminating the need for constant database lookups. The server validates the token’s signature to ensure it hasn’t been tampered with. Then, each subsequent request from the client includes the JWT. Upon successful login, the server creates a JWT containing user information and a signature to verify its authenticity. The server authenticates the user, often by checking the entered credentials against a database. Like before, users would log in with their credentials. JWT, especially when used as a session, attempts to eliminate the subsequent database lookup. This process often slows down the application. The problem with this approach is that for every request, the server takes a round trip to the database.

The server looks up the session ID in its database to identify the user and determine their authorization level. This session ID is then stored on the user’s device.įor each subsequent user request, the session ID is sent to the server either in a cookie or as a header. Upon successful authentication, a unique session identifier is generated and sent back to the client. To understand the problem JWT aims to solve, let’s look at how we traditionally handle authentication and authorization.ĭuring the login process, users log in with their credentials. HTTPS not only safeguards the confidentiality of JWT contents during transmission but also provides a broader layer of protection for data in transit. It is strongly advised to use JWTs with HTTPS, a practice that extends to general web security. The reason is that the JWT can be seen by anyone who intercepts the token because it’s serialized, not encrypted. It’s important to note that a JWT guarantees data ownership but not encryption. This is possible because each JWT is signed using cryptography to guarantee that its contents have not been tampered with during transmission or storage. These claims help share specific details between the parties involved.Īt its core, a JWT is a mechanism for verifying the authenticity of some JSON data. They contain information (claims) encoded in the JSON format. JSON Web Tokens (JWTs) are a standardized way to securely send data between two parties. In this article, we will explore JWT authentication, its limitations, and scenarios where its implementation proves invaluable. Some caution against their use, while others view them as an excellent authentication method. However, as with any technology, JWTs have sparked controversy. Among them, JSON Web Tokens (JWTs) have emerged as a popular choice over the years. Various tools and packages have been developed to facilitate this. Editor’s note: This JWT authentication tutorial was last updated on 5 December 2023 to discuss some of the efficiencies of JWT authentication, including token invalidation and size constrains.Įnsuring the security of user data and establishing secure communication between servers and clients is a critical aspect of web development.

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