How to Use the JWT Parser:
Paste a JWT token into the input field. The token consists of three parts separated by dots (header.payload.signature). Click Parse to decode the token and view its header, payload, and signature information. The tool will display the decoded JSON data in a readable format, making it easy to inspect token claims and expiration dates.
API Authentication
Debug JWT tokens used in REST API authentication to verify claims, expiration, and token structure.
WordPress Security
Inspect JWT tokens in WordPress authentication plugins and custom login systems to ensure proper token validation.
Token Validation
Verify JWT token structure and claims before implementing authentication logic in web applications.
How Do JWT Tokens Work?
JWT tokens consist of three Base64-encoded parts: header (algorithm and token type), payload (claims and data), and signature (verification). The parser decodes these parts to reveal the token’s structure and contents.
Token Structure
JWTs have three parts separated by dots: header.payload.signature. Each part is Base64-encoded JSON data.
Header
Contains token metadata like the signing algorithm (HS256, RS256, etc.) and token type (JWT).
Payload
Contains claims (user data, expiration, issuer) and custom data. This is the main content of the token.
Signature
Used to verify the token hasn't been tampered with. Created by signing the header and payload with a secret key.
Using JWT Tokens in JavaScript:
function parseJWT(token) {
const parts = token.split('.');
const header = JSON.parse(atob(parts[0]));
const payload = JSON.parse(atob(parts[1]));
return { header, payload };
}
const token = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...';
const decoded = parseJWT(token);
console.log(decoded);{ header: {...}, payload: {...} } Parse and decode JWT token to view header and payload
Frequently asked questions
The tool decodes and displays token contents, but signature verification requires the secret key, which should never be shared or entered into web tools.
JWT tokens contain a header (algorithm info), payload (claims like user ID, expiration), and signature (for verification).
Only paste tokens you own or have permission to inspect. Never share tokens publicly as they may contain sensitive information.
Collect Better Feedback with Userback
This JWT parser helps you inspect authentication tokens efficiently, but gathering feedback about authentication issues and security problems requires comprehensive context. Userback captures detailed visual feedback when users report authentication failures, token validation errors, or security concerns. With automatic screenshot capture, browser information, console logs, and network requests, you get complete visibility into authentication-related issues. When developers need to report JWT parsing errors or suggest improvements to authentication workflows, Userback enables them to submit detailed feedback that includes token context (without sensitive data) and all technical details in a single shareable report.