wtf is aws-jwt-verify?

AWS JWT Verify is a library that helps your application confirm whether a login token is genuine. When a user logs in through a service like Amazon Cognito, they receive a token that proves their identity. Before your app grants access to protected data, it needs to check that this token is real, hasn't been tampered with, and hasn't expired. This library does that checking for you. At a high level, you create a verifier object with a few details about your login provider. Then, you hand that verifier a user token, and it either confirms the token is valid and returns the user's information, or it throws an error. Behind the scenes, the library fetches the cryptographic keys from your identity provider and uses them to mathematically verify the token's signature. It also automatically checks standard security claims, like whether the token has expired or if it was actually issued by the provider you expect. It handles key rotations automatically, so you don't have to worry about updating keys when your login provider rotates them. This tool is built for developers creating backend APIs on AWS, especially those using AWS Lambda or serverless functions to handle web requests. For example, if you run an e-commerce site where logged-in customers can view their order history, you might use this library in a Lambda function to check the token attached to their request. If the token checks out, the function lets them through to retrieve their data. If not, they are blocked. It also works with other standard login providers beyond Amazon, and can be used in modern web browsers. A notable thing about the project is its focus on doing one thing well and doing it securely. It has zero runtime dependencies, meaning it bundles all its own necessary code, which keeps the package lightweight and reduces potential security risks. It is also designed to be opinionated about security, guiding users toward best practices by requiring them to check important claims like the token's issuer and audience.