JWT Decoder
Free online JWT Decoder. Simple, fast, and secure tool running in your browser.
What is the JWT Decoder?
The JWT Decoder is a free browser-based tool that instantly decodes JSON Web Tokens (JWT) into their readable components — header, payload, and signature. JWTs are the industry-standard method for securely transmitting authentication and authorization data between services in modern web applications, mobile apps, and APIs.
This tool automatically detects the signing algorithm, checks token expiration status, displays issued-at timestamps in human-readable format, and lets you copy each decoded section individually. All decoding happens locally in your browser — your tokens are never sent to any external server.
How to Decode a JWT Token
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1
Paste Your JWT Token
Copy the JWT string from your API response, browser DevTools, or authentication header and paste it into the input field.
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2
Click Decode JWT
The tool splits the token into its three base64url-encoded parts and decodes them into readable JSON.
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3
Inspect the Results
Review the header (algorithm and type), payload (claims, user data, permissions), signature, and expiration status. Copy any section with one click.
Real-World Use Cases
Authentication Debugging
Quickly inspect JWT payloads to verify user claims, roles, and permissions when debugging login flows or API authentication issues.
Token Expiration Checks
Instantly check if a JWT has expired without writing code. See exact expiration and issued-at dates in human-readable format.
API Integration Testing
When integrating third-party OAuth providers (Google, GitHub, Auth0), decode their JWT responses to understand the structure and available claims.
Frequently Asked Questions
What is a JWT?
A JSON Web Token (JWT) is a compact, URL-safe token format used to securely transmit information between parties. It consists of three base64url-encoded parts separated by dots: header, payload, and signature.
Is it safe to decode JWTs in a browser tool?
Yes — decoding a JWT only reads its contents. It does not verify or validate the signature. This tool processes everything locally in your browser, so your tokens never leave your device. However, never share production tokens publicly.
Can this tool verify JWT signatures?
This tool decodes and displays JWT contents but does not verify cryptographic signatures. Signature verification requires the signing secret or public key, which should never be shared in a client-side tool.
What do the exp and iat claims mean?
exp (expiration time) is the Unix timestamp after which the token should not be accepted. iat (issued at) is the Unix timestamp when the token was created. This tool converts both to human-readable dates automatically.
What algorithms are supported?
This decoder reads JWTs signed with any algorithm (HS256, RS256, ES256, etc.) since decoding does not require the signing key. The algorithm is displayed in the decoded header section.