JWT Parser Online Tool

Input JWT token to decode Header and Payload, display all claims information, supports multiple signature algorithms

JWT Parser

Features

  • Complete Parsing: Parse JWT Header, Payload and Signature three parts, fully display token structure
  • JSON Formatting: Automatically format JSON data, indent display, clear and readable
  • Time Decoding: Automatically decode iat, exp, nbf etc. timestamps, convert to readable date time format
  • One-click Copy: Support copying entire Header or Payload, quick paste to use
  • Real-time Parsing: Auto parse after entering JWT, no need to click button, instant view results
  • Local Parsing: All parsing done locally in browser, not uploaded to server, protects privacy

How to Use

1

Enter JWT Token

Paste the JWT token to parse in the input box, token format is usually three parts separated by dots of Base64Url encoded strings.

2

View Decoded Result

After entering, system will automatically parse, separately display Header, Payload, Signature and time information.

3

Copy to Use

Click copy button of each part, can copy corresponding content to clipboard, quick paste to code or document.

Use Cases

API Debugging

Parse JWT token returned by API, view token content and expiration

Issue Investigation

Investigate authentication issues, check if token is valid or expired

Learning Research

Learn JWT structure, understand meaning and function of each part

Security Audit

Audit JWT token content, check if contains sensitive information

User Authentication

Analyze user identity token, view user info and permission claims

Backend Development

Backend development debugging JWT generation and validation logic

JWT Introduction

JWT (JSON Web Token) is an open standard for securely transmitting information between parties.

What is JWT?

JWT (JSON Web Token) is an open standard (RFC 7519) for securely transmitting information as JSON objects between parties. This information can be verified and trusted through digital signatures. JWT can be signed using a key (like HMAC algorithm) or using RSA or ECDSA public/private key pairs.

JWT Structure

JWT consists of three parts, separated by dots (.):

  • Header: Usually consists of two parts: token type (JWT) and signing algorithm (like HMAC SHA256 or RSA)
  • Payload: Contains claims, statements about entity (usually user) and other data
  • Signature: Using encoded header, encoded payload and key, generated through specified algorithm

Common Claims

  • iss (Issuer): Token issuer
  • sub (Subject): Subject, usually user ID
  • aud (Audience): Token audience
  • iat (Issued At): Token issue time
  • exp (Expiration Time): Token expiration time
  • nbf (Not Before): Token effective time
  • jti (JWT ID): Unique identifier

JWT Security Notes

When using JWT note: 1) Don't put sensitive info in Payload, because Base64Url is encoding not encryption; 2) Set reasonable expiration time; 3) Use HTTPS transmission; 4) Choose secure signing algorithm; 5) Verify signature, prevent tampering.

Frequently Asked Questions

Q: Is JWT parser free?
A: Completely free, no registration login required, no usage limit, open webpage to use. All parsing done locally in browser, not uploaded to server, protects your data privacy.
Q: Can parsed JWT be modified?
A: This tool only provides parsing function, doesn't support modification. If Payload content is modified, signature will be invalid, server validation will fail.
Q: Is JWT Payload encrypted?
A: No. JWT Payload only uses Base64Url encoding, can be easily decoded. Therefore, don't store passwords, keys etc. sensitive info in JWT. JWT signature is for verifying integrity, not encrypting content.
Q: What's the difference between JWT and Session?
A: Session is server-side storing user state, client only saves Session ID; JWT is client-side storing all info, server only needs to verify signature. JWT is more suitable for distributed systems and cross-domain authentication, but cannot actively invalidate is its drawback.
Q: What if JWT expires?
A: After JWT expires need to re-acquire. Common practice is using Refresh Token mechanism: when Access Token expires, use Refresh Token to get new Access Token, without user re-login.
Q: Which signing algorithms are supported?
A: JWT supports multiple signing algorithms, common ones are HS256 (HMAC-SHA256), RS256 (RSA-SHA256), ES256 (ECDSA-SHA256) etc. This tool supports parsing Header and Payload of all standard JWT tokens.
Q: Will entered JWT be recorded?
A: No. All JWT parsing operations are done locally in your browser, JWT content will not be uploaded to any server, not recorded, completely protects your data privacy and security.

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