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About this Tool
A JWT Decoder is a tool that breaks down a JSON Web Token into its three core parts: Header, Payload, and Signature.
It converts Base64URL-encoded data into human-readable JSON so developers can inspect authentication data such as user ID, roles, expiration time, and issuer.
Advanced JWT tools also analyze security risks and validate token integrity.
JWT (JSON Web Token) is widely used for authentication and secure data exchange in modern web applications.
Our free JWT Decoder & Security Analyzer helps you instantly decode tokens into readable format, inspect header, payload, and signature, and analyze security risks like expired tokens, missing claims, and tampering attempts.
How to use
- Paste your JWT token into the input field
- The tool automatically decodes header and payload
- View token details like issuer, subject, and expiration
- Check security analysis for risks like missing exp or alg:none
- Use the tabs to explore decoded data, claims, and time info
- Copy or export the decoded result for debugging or development use
Benefits
- Instantly decode JWT tokens without backend tools
- Debug authentication issues in APIs and frontend apps
- Inspect user roles, permissions, and claims easily
- Detect security risks like expired tokens or missing signatures
- Validate OAuth and authentication flows during development
- Improve security awareness by analyzing token structure
FAQs
What is a JWT token?
A JWT (JSON Web Token) is a compact token used for securely transmitting information between two parties. It contains a header, payload, and signature.
Is JWT decoding safe?
Yes. Decoding a JWT is safe because it only converts encoded data into readable format. It does not require the secret key and does not modify the token.
Can I see the password in a JWT token?
No. JWT tokens should never contain passwords. They usually contain user ID, roles, and metadata, but not sensitive secrets.
What happens if a JWT is expired?
If a JWT is expired, the server will reject it during authentication. The decoder will also show it as expired based on the 'exp' claim.
Can JWT tokens be modified?
Yes, but modifying a JWT without the correct signature will make it invalid. The server will reject tampered tokens.
What is alg:none vulnerability?
It is a security issue where a JWT is unsigned or incorrectly configured, allowing attackers to bypass signature verification.
Is my JWT data stored anywhere?
No. All decoding happens locally in your browser. Your token is never sent to a server or stored.