Offline JWT Decoder

Decode JSON Web Tokens (JWT) 100% locally and securely. Breaks down headers, payload, signatures, and checks expiration timestamps in real time.

JWT Input

Ingresa un token para analizar su firma y fechas de vigencia.

Decoded segments

Invalid JWT. Ensure the token has three dot-separated segments.
Header: Metadata 
{}
Payload: Claims & Data 
{}
Signature: HMAC / RSA Verification 
Signature segment is validated offline for structure.

User Guide: Understanding and Securely Decoding JSON Web Tokens (JWT)

A **JSON Web Token (JWT)** is a widely-used open standard (RFC 7519) that defines a compact, self-contained mechanism for securely transmitting assertions or data claims between systems as a JSON object. JWTs are the industry standard for securing modern RESTful APIs and microservices during client authentication and single sign-on (SSO).

A JSON Web Token consists of three distinct segments delimited by periods (.):

  • Header: Specifies metadata about the token, such as token type and cryptographic signing algorithm (e.g., HMAC SHA256 or RSA).
  • Payload: Encodes claims or context information (such as user ID, role scopes, and lifespan boundaries).
  • Signature: Combines the encoded header and payload segments with a server secret using the specified algorithm to verify message integrity and sender identity.
Critical Security Best Practice
Notice: The first two segments (Header & Payload) of a JWT are only **Base64Url encoded**, not encrypted. Anyone who intercepts a token can reconstruct the underlying JSON object effortlessly. **Consequently, never place sensitive credentials, credit card details, or private keys inside a JWT claim set.**
How to use this Offline JWT Parser
  1. Paste your complete JWT into the input field on the left card.
  2. Instantly inspect the decoded sections on the right card, color-coded for fast readability (Red for Header, Purple for Payload, and Blue for Signature).
  3. Check the status panel on the lower left to view formatted expiration timestamps (exp) and determine if the token is active or expired.
Data Privacy & Security Guaranteed
100% Offline-First Sandbox: Pasting live bearer tokens into internet decoders can lead to account hijackings or credential leaks. Our utility performs all Base64Url parsing **strictly client-side in your local browser sandbox**. No token data leaves your device, keeping your production tokens completely private.