Dev & Data ToolboxJWT Decoder & Verifier
JWT Token
Signature Verification
Example JWTs
Header
Payload
Signature
JWT Decoder & Verifier - Decode and Verify JSON Web Tokens
Our JWT Decoder & Verifier is a comprehensive tool designed for developers to decode, analyze, and verify JSON Web Tokens (JWTs). With real-time decoding, intelligent claim interpretation, and signature verification capabilities, this tool provides everything you need to work with JWTs securely and efficiently.
How to Use the JWT Decoder
Paste Your JWT
Copy your JWT token and paste it into the input field. The tool will automatically decode it in real-time.
Review Decoded Data
Examine the decoded header, payload, and signature. Timestamps are automatically converted to human-readable format.
Verify Signature (Optional)
Enter your secret key or public key to verify the token's signature and ensure authenticity.
Copy Results
Use the copy buttons to easily copy decoded JSON, headers, or the original token for further use.
JWT Structure - Understanding the Components
Header
Contains metadata about the token type and signing algorithm (e.g., HS256, RS256).
Payload
Contains the actual data (claims) including user information and token metadata.
Signature
Cryptographic signature that verifies the token's authenticity and integrity.
Format: header.payload.signature
Registered Claims - Standard JWT Fields
exp (Expiration Time)
Unix timestamp when the token expires. Our tool shows both timestamp and human-readable date.
iat (Issued At)
Unix timestamp when the token was issued. Shows relative time like "5 minutes ago".
nbf (Not Before)
Unix timestamp before which the token should not be accepted.
sub (Subject)
The subject of the token, typically a user ID or unique identifier.
iss (Issuer)
The issuer of the token, usually the application or service that created it.
aud (Audience)
The intended audience of the token, specifying who should accept it.
Key Features - What Makes Our Tool Special
Real-time Decoding
Instant JWT parsing as you type, with immediate visual feedback.
Intelligent Claim Interpretation
Automatic timestamp conversion and status indicators for expiration times.
Signature Verification
Verify token authenticity using HMAC or RSA algorithms with your keys.
One-click Copy
Easy copying of decoded JSON, headers, payloads, and the original token.
Example Tokens
Pre-loaded example JWTs for testing and learning purposes.
Privacy First
All processing happens in your browser. No data is sent to our servers.
Frequently Asked Questions
What is a JWT?
A JSON Web Token (JWT) is a compact, URL-safe means of representing claims between parties. It consists of three parts: header, payload, and signature, separated by dots.
Is it safe to decode JWTs?
Yes! JWT headers and payloads are Base64Url encoded, not encrypted. Anyone can decode them. The signature is what provides security and authenticity verification.
How does signature verification work?
The tool uses the Web Crypto API to verify signatures. For HMAC algorithms, you provide the secret key. For RSA/ECDSA, you provide the public key in PEM format.
What if my JWT is expired?
The tool will clearly show "❌ EXPIRED" status for expired tokens and display how long ago it expired. You'll need to obtain a new token from your authentication service.
Technical Information
Supported Algorithms: HS256, HS384, HS512 (HMAC), RS256, RS384, RS512 (RSA), ES256, ES384, ES512 (ECDSA)
Encoding: Base64Url decoding for header and payload sections
Verification: Web Crypto API for cryptographic operations
Privacy: All processing performed client-side, no data transmitted
Browser Support: Modern browsers with Web Crypto API support
Privacy & Security
🔒 Client-Side Processing: All JWT decoding and verification happens in your browser. No token data is ever sent to our servers.
🛡️ No Data Storage: We don't store, log, or transmit any of your JWT tokens or keys.
🔐 Secure Verification: Signature verification uses the Web Crypto API for secure cryptographic operations without exposing your keys.
🌐 Open Source: The tool is built with transparency in mind, allowing you to verify the security implementation.