JWT Decoder
Need to see what data is inside an authentication token? Our free JWT Decoder instantly parses JSON Web Tokens, allowing you to securely inspect the header and payload claims.
What is the JWT Decoder Online - Parse JSON Web Tokens?
The JWT (JSON Web Token) Decoder is a cybersecurity and developer tool. It takes a Base64URL-encoded JWT string and decodes it, revealing the readable JSON objects contained within the token's Header and Payload sections.
How to use the JWT Decoder Online - Parse JSON Web Tokens
- Paste your full JWT string (Header.Payload.Signature) into the input box.
- The tool instantly decodes the string.
- The readable JSON Header and Payload are displayed in beautifully formatted code blocks.
Example
You paste a long string starting with `eyJhbGci...`. The tool decodes it and reveals the payload contains: `{"sub": "1234567890", "name": "John Doe", "iat": 1516239022}`.
Understanding Your Results
You can now read the claims inside the token, such as the user ID (`sub`), the token expiration time (`exp`), and the algorithm used (`alg`). This is crucial for debugging authentication flows.
Common Use Cases
- Auth Debugging: Figuring out why a user is getting logged out by checking the `exp` (expiration) timestamp inside their token.
- API Development: Verifying that your backend is successfully embedding the correct user roles into the JWT payload.
- Security Audits: Inspecting tokens to ensure sensitive data (like plain text passwords) is not accidentally being encoded in the payload.
How it Works
A JWT consists of three parts separated by periods (`.`). The tool splits the string at the periods. It takes the first two parts (Header and Payload), decodes them from Base64URL format into standard text, and parses them as JSON.
Tips & Accuracy Notes
- •This tool ONLY decodes the token so you can read it. It does NOT verify the cryptographic signature. A decoded token might still be invalid or expired.
- •Anyone can decode a JWT. You must never put secret or sensitive information inside a JWT payload unless the token itself is encrypted (JWE).
Frequently Asked Questions
Is it safe to paste my JWT here?
Yes. This tool runs entirely in your local browser. Your JWT is never sent to our servers. However, as a best practice, never paste production access tokens into any online tool if you can avoid it.
Why can't I edit the token?
If you edit the payload of a JWT, the cryptographic signature will instantly become invalid. You would need the server's private secret key to generate a new valid signature.
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Disclaimer: Decoding occurs 100% client-side via JavaScript. This tool does not perform cryptographic signature validation.