Debug your authentication flow. Instantly decode JSON Web Tokens to inspect header algorithms, read payload claims, and verify expiration timestamps safely.
Execute complex Base64URL parsing locally without sending sensitive bearer tokens to external servers.
The parser automatically splits the token at the period `.` delimiters, separating the massive string into the distinct Header, Payload, and Signature components.
A JWT is NOT encrypted; it is just encoded. The engine instantly decodes the Base64URL string back into human-readable JSON to expose the hidden claims.
Pasting a production Bearer Token into a random website is extremely dangerous. This tool executes the decoding entirely inside your local browser to prevent token theft.
A JSON Web Token (JWT) is an open industry standard used to securely transmit information between two parties. It is the foundational technology behind modern, stateless authentication systems. When you log into an application, the server generates a JWT containing your identity and sends it to your browser. You then attach that token to every future API request as proof of who you are.
If you look at a raw JWT, it appears to be a massive string of random gibberish. However, an online JWT decoder reveals that it is actually composed of three distinct parts separated by a period (.):
HS256 (HMAC with SHA-256) or RS256 (RSA Signature).The most catastrophic mistake a junior developer can make is assuming a JWT is encrypted. It is not.
The Header and the Payload are simply converted using Base64URL encoding. This is done to ensure the data safely travels over HTTP without breaking. Anyone on the internet can copy your JWT, paste it into a decoder, and read everything inside the payload.
You must never put Personally Identifiable Information (PII) like social security numbers, passwords, or credit card data inside the payload. If you do, you are exposing that data to anyone who can view the browser's local storage.
In the past, servers used Session Cookies. The server kept a massive database of every logged-in user. Every time you made a request, the server had to query the database to see if your cookie was valid.