JWT Token Decoder Online Tool

Decode JSON Web Tokens with our free online tool. View token contents without server processing.

JWT Token

Decoded Header

Decoded Payload

Signature Verification

How to Use This JWT Token Decoder Tool

Decoding JWT Tokens

  1. Enter your JWT token using either:
    • Paste directly into the input box
    • Use the paste button
  2. Automatic decoding happens instantly as you paste
  3. View decoded components in the Header and Payload sections
  4. Copy decoded results
    • Use the copy buttons
    • Or standard Ctrl+C/Cmd+C

Verifying Token Signatures

  1. Enter your secret key in the verification section if you want to validate the signature
  2. The tool will automatically verify the token signature using the provided key
  3. View verification status
    • Green checkmark for valid signatures
    • Red warning for invalid signatures
  4. Note: Signature verification requires the correct algorithm and key

Supported JWT Features

Component
Supported Features
Details
Header
All standard fields
alg, typ, kid, etc.
Payload
Standard and custom claims
sub, iss, exp, iat, etc.
Algorithms
HS256, HS384, HS512
HMAC with SHA-2
Token Types
Standard JWTs
Access tokens, ID tokens

Key Technical Details

JWT Structure

  • Header: Contains metadata about the token type and signing algorithm
  • Payload: Contains claims (statements about the subject)
  • Signature: Used to verify the token wasn't altered
  • Base64URL: All components are Base64URL encoded

Common Use Cases

  • Authentication: Securely transmit user identity between services
  • API Authorization: Access control for web services
  • Information Exchange: Securely transmit information between parties
  • Session Management: Stateless session tokens

Important Security Notes

  • Sensitive Data: JWTs are not encrypted by default - don't store sensitive data in tokens
  • Signature Verification: Always verify tokens in production environments
  • Expiration: Check exp claim to prevent use of expired tokens
  • Privacy: Tokens are processed in your browser only - never sent to our servers

Frequently Asked Questions

Decoding JWT tokens is essential for debugging authentication issues, verifying token contents during development, and understanding the claims being passed between services. It helps developers ensure their authentication system is working correctly.

All processing happens directly in your browser - your tokens are never sent to any server. However, you should never paste production tokens with sensitive information into any tool. Use test tokens for development purposes only.

This tool currently supports HMAC-based algorithms (HS256, HS384, HS512) which use a shared secret. RS256 uses asymmetric public/private key cryptography which requires the public key for verification. For RSA-based algorithms, you would need specialized tools that can handle public key cryptography.