JWT Decoder
Decode and validate JSON Web Tokens (JWT)
Note: Decoding happens in your browser. Your token is never sent to any server.
About JWT Decoder
JSON Web Tokens (JWT) are an industry standard (RFC 7519) for securely transmitting information between parties as a JSON object. This tool decodes the header, payload, and signature without validation.
â ī¸ Security Warning: Never share sensitive tokens publicly. This tool only decodes - it does not verify signatures.
Privacy & Security
All JWT decoding happens entirely in your browser using JavaScript. Your tokens are never uploaded to our servers, transmitted over the network, stored in databases, or logged anywhere. When you close the page, your tokens are permanently gone. Completely private and secure for even the most sensitive authentication tokens.
About JWT Decoder
Decode and analyze JSON Web Tokens (JWTs) with our free online decoder. Whether you're a backend developer debugging authentication issues, a frontend engineer inspecting API tokens, a security professional auditing token claims, or a student learning about JWT architecture, our tool instantly decodes the header, payload, and signature sections of any JWT. Perfect for troubleshooting OAuth flows, verifying token contents, checking expiration times, and understanding token structure without writing code.
Key Features
Instant Decoding
Decode JWT tokens in real-time as you paste them
Three-Part Breakdown
See header, payload, and signature components separately and clearly
JSON Formatting
Pretty-printed JSON with syntax highlighting for easy reading
Claim Inspection
View all claims including iss, sub, aud, exp, nbf, iat, and custom claims
Expiration Check
Automatically detect and highlight expired tokens with timestamps
Algorithm Display
Shows signing algorithm (HS256, RS256, ES256, etc.) from header
Base64 Decoder
Decodes Base64URL-encoded header and payload automatically
Copy Components
Copy individual sections or the entire decoded JWT with one click
Validation Warnings
Alerts for malformed tokens or invalid Base64 encoding
Privacy First
All decoding happens in browser - tokens never sent to servers
How to Use the JWT Decoder
Paste Your JWT
Copy your JWT token string and paste it into the input field
View Decoded Parts
See the header, payload, and signature automatically decoded and formatted
Inspect Claims
Review token claims, expiration time, issuer, audience, and custom data
Debug or Verify
Use the decoded information to troubleshoot authentication or verify token contents
Frequently Asked Questions
What is a JWT and what does it contain?
A JSON Web Token (JWT) is a compact, URL-safe string that represents claims to be transferred between two parties. It has three parts separated by dots: Header (algorithm and token type), Payload (claims like user ID, permissions, expiration), and Signature (cryptographic verification). JWTs are commonly used for authentication and information exchange in modern web applications.
Can this tool verify JWT signatures?
This decoder displays the signature component but does not cryptographically verify it, as that requires the secret key or public key used to sign the token. The tool is designed for decoding and inspecting token contents, not for security validation. Signature verification should be done server-side with access to the proper keys.
What does 'exp' in the payload mean?
'exp' (expiration time) is a standard JWT claim containing a Unix timestamp indicating when the token expires. After this time, the token should be considered invalid and rejected by APIs. Our decoder automatically shows if a token is expired based on the current time.
Why are there three parts separated by dots?
The three-part structure (header.payload.signature) allows JWTs to be self-contained and verifiable. The header describes how the token is signed, the payload contains the actual data claims, and the signature proves the token hasn't been tampered with. Each part is Base64URL-encoded for safe transmission in URLs and HTTP headers.
Can I use this to decode tokens from any authentication system?
Yes! Our decoder works with JWTs from any system - Auth0, Firebase, Keycloak, AWS Cognito, custom backends, etc. As long as it's a valid JWT following the RFC 7519 standard, the tool will decode it.
Is this JWT decoder free?
Yes! Our JWT decoder is completely free to use with unlimited token decoding and no registration required.
Will my JWT tokens be stored or sent anywhere?
No. All decoding happens entirely in your browser using JavaScript. Your tokens are never sent to our servers, logged, stored in databases, or transmitted anywhere. Completely private and secure.
Does it work on mobile devices?
Absolutely! The decoder is fully responsive and works perfectly on smartphones, tablets, and desktop computers for on-the-go debugging.
Common Use Cases
- API Debugging: Decode access tokens to verify claims and troubleshoot 401 authentication errors
- OAuth Flow Testing: Inspect ID tokens and access tokens during OAuth 2.0 and OpenID Connect flows
- Token Expiration Check: Quickly determine if a token is expired without making API calls
- Security Audits: Analyze JWT structure and claims for security best practices compliance
- Backend Development: Verify that your server is generating JWTs with correct header and payload
- Frontend Debugging: Inspect tokens received from authentication endpoints before storing
- Integration Testing: Validate JWT format and claims in automated API integration tests
- Learning JWTs: Study JWT structure and understand how they encode authentication data
Why Use Our JWT Decoder?
Debugging JWT authentication shouldn't require installing libraries, writing code, or exposing sensitive tokens to third-party servers. Our free JWT decoder gives you instant visibility into token contents with a simple paste action, making authentication troubleshooting fast and secure. Whether you're tracking down why a user can't access a resource, verifying that your authentication server is issuing correct claims, or learning how JWTs work under the hood, you'll appreciate the immediate feedback, clear formatting, and complete privacy. No more console.logging base64 strings or manually decoding tokens - just paste and understand your JWT structure instantly.