JWT Decoder
Decode JSON Web Tokens instantly and completely locally. Your sensitive tokens are never sent to a server.
What is a JWT Decoder?
A JWT (JSON Web Token) decoder is a tool that parses and displays the contents of a JWT without needing the secret key. JWTs consist of three Base64URL-encoded parts: the Header (algorithm and token type), the Payload (claims like user ID, expiration, and permissions), and the Signature. Our secure JWT decoder breaks down each part, showing you the decoded header and payload in formatted JSON. Unlike other JWT decoders, this tool runs 100% in your browser — your tokens are never sent to any server.
How to Decode a JWT Token Online
- 1Paste your JWT
Copy the full JWT string (starts with "eyJ...") and paste it into the input field above.
- 2View decoded sections
The decoder instantly shows the Header (algorithm info) and Payload (claims data) in formatted JSON.
- 3Check expiration
The "exp" claim shows when the token expires. The decoder highlights if the token is expired.
- 4Copy decoded data
Copy the decoded header or payload JSON for debugging or documentation purposes.
Frequently Asked Questions
Is it safe to paste my JWT token here?
Yes. DevDeck decodes JWTs entirely in your browser using JavaScript. The token is never transmitted to any server, never logged, and never stored. It exists only in your browser's memory and is discarded when you leave the page.
Can this tool verify JWT signatures?
This tool decodes and displays JWT contents. Signature verification requires the secret key or public key, which we intentionally do not ask for to maximize your security.
What is a JWT used for?
JSON Web Tokens are widely used for authentication and authorization in web applications. After a user logs in, the server issues a JWT containing user claims. The client sends this token with subsequent requests to prove identity.
What does each part of a JWT mean?
A JWT has three parts separated by dots: the Header (specifies the signing algorithm like HS256 or RS256), the Payload (contains claims like user ID, roles, and expiration time), and the Signature (used to verify the token hasn't been tampered with).
Why Use DevDeck?
JWT tokens often contain sensitive user data and permissions. Other online decoders send your tokens to their servers for processing. DevDeck decodes everything in-browser using pure JavaScript — your authentication tokens never leave your machine.