JWT Decoder
Decode JWT header, payload, and signature locally with expiry checks. Use this free online tool directly in your browser.
JWT Token
Decoded locally — never sent to a server
What is JWT Decoder?
A JSON Web Token (JWT) is a compact, URL-safe token format widely used for authentication and authorization in modern web applications. It consists of three Base64URL-encoded segments — header, payload, and signature — separated by dots. The header declares the signing algorithm, the payload carries claims (user ID, roles, expiry, and custom data), and the signature lets a server verify the token was not tampered with. JWTs are issued by identity providers like Auth0, Cognito, and Firebase, and are sent in the Authorization header of API requests as Bearer tokens. This decoder processes your token entirely in the browser — the raw token never leaves your device, making it safe to inspect production tokens containing real user data. Use it to verify expiry times, check claim values, identify the signing algorithm, and debug authentication issues without risking token exposure.
How to use
- 1
Paste or enter your data in the JWT Decoder input area.
- 2
Run the conversion, generation, or validation action.
- 3
Copy or download the result for your project workflow.
Common Use Cases
- 1
Debug authentication failures by checking claim values like sub, aud, and iss from your identity provider
- 2
Verify token expiry in real time with the live countdown — no manual date math needed
- 3
Inspect the signing algorithm (alg) to confirm your backend is not accepting the none algorithm
- 4
Compare tokens across dev, staging, and production environments to spot configuration drift
- 5
Use batch mode to decode multiple tokens from a multi-service architecture in one pass
Try an Example
Example Input
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NSIsImV4cCI6MjYwMDAwMDAwMCwiaWF0IjoxNzAwMDAwMDAwfQ.signature
Frequently Asked Questions
What is JWT Decoder?
JWT Decoder is a free browser-based utility on Bite Size Tools. Decode JWT header, payload, and signature locally with expiry checks.
Is JWT Decoder safe to use with sensitive data?
Yes. Tool processing runs in your browser, so your input is not sent to a server by default in this app.
Can I use JWT Decoder for production work?
Yes. You can use the output directly in development and production workflows after validating it with your project requirements.
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