A JWT Parser is a tool that takes a JSON Web Token (JWT) as input and decodes it to reveal the contents of the header and payload sections. JWTs are encoded in Base64url format and consist of three parts: header, payload and signature.

Parsing a JWT allows developers and testers to inspect the claims and metadata contained within the token without validating the signature.

You should use a JWT Parser when you need to examine the contents of a JWT, such as during development, debugging or testing of authentication and authorization mechanisms in web applications and APIs. It helps in verifying that the correct claims are included, that they have the expected values and that the token is structured properly.

This is particularly useful for developers and QA engineers performing automated tests on platforms like TestingBot, where ensuring correct token generation and handling across different browsers and devices is essential.

A JWT Parser can assist in automated testing by allowing test scripts to programmatically inspect and validate the contents of JWTs generated by an application. This ensures that the tokens contain the correct claims and that sensitive information is not unintentionally exposed.