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JWT Decoder

Decode and inspect JSON Web Tokens instantly

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About JWT Decoder

The JWT Decoder is a powerful online tool for decoding and inspecting JSON Web Tokens (JWT). Whether you're debugging authentication issues, validating token structure, or learning about JWT, this tool provides instant, detailed analysis of your tokens with a clean, intuitive interface.

What is JWT?

JSON Web Token (JWT) is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. JWTs are commonly used for authentication and information exchange in modern web applications, mobile apps, and APIs.

JWT Structure

  • Header: Contains metadata about the token type and the cryptographic algorithm used to secure it (e.g., HS256, RS256)
  • Payload: Contains the claims - statements about the user and additional data. This is the main body of the token
  • Signature: Used to verify that the token hasn't been tampered with. Created by encoding the header and payload with a secret key

Common JWT Claims

  • iss (Issuer) - Who created and signed the token
  • sub (Subject) - The subject of the token (usually user ID)
  • aud (Audience) - Who the token is intended for
  • exp (Expiration Time) - When the token expires (Unix timestamp)
  • iat (Issued At) - When the token was created (Unix timestamp)
  • nbf (Not Before) - Time before which the token is not valid
  • jti (JWT ID) - Unique identifier for the token

How to Use This Tool

  1. Paste Token: Copy your JWT token from your application, API response, or browser and paste it into the input field
  2. Automatic Decoding: The token is decoded instantly as you paste, showing all three parts with syntax highlighting
  3. Review Information: Check the header for algorithm, payload for claims, and token information for expiration status
  4. Copy Parts: Use the copy buttons to copy individual parts (header, payload, signature) for further analysis

Features

  • Instant Decoding: Real-time JWT decoding as you type or paste
  • Visual Color Coding: Each token part is color-coded for easy identification
  • Expiration Detection: Automatically checks if the token is expired and displays status
  • Copy to Clipboard: One-click copying of entire token or individual parts
  • Error Handling: Clear error messages for invalid tokens with helpful guidance
  • Claim Parsing: Automatic parsing and display of standard JWT claims
  • Privacy First: All decoding happens in your browser - tokens never leave your device
  • Mobile Friendly: Responsive design works perfectly on all devices

Common Use Cases

  • Authentication Debugging: Debug login issues by inspecting token contents and expiration times
  • API Development: Verify JWT tokens issued by your authentication server during development
  • Security Auditing: Review token structure and claims for security best practices
  • Learning: Understand how JWT works by decoding real tokens and seeing their structure
  • Token Validation: Check if tokens contain the expected claims and haven't expired

Privacy & Security

100% Client-Side: All JWT decoding happens entirely in your browser using JavaScript. Your tokens are never sent to any server or stored anywhere. This tool is completely safe for decoding production tokens and sensitive authentication data. The decoded information is only visible to you and disappears when you close or refresh the page.

Note: While this tool decodes JWTs, it doesn't verify signatures. Signature verification requires the secret key, which should never be shared or entered into online tools for security reasons.