JWT Builder

Build, encode, decode, and validate JSON Web Tokens (JWT) with this free online tool.

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About This Tool

The JWT Builder is a comprehensive online tool for working with JSON Web Tokens. Create JWT tokens by specifying header parameters (like algorithm and token type), payload data (claims), and a secret key. The tool supports HMAC algorithms (HS256, HS384, HS512) for signing. You can also decode existing JWT tokens to view their header and payload contents. All processing happens client-side in your browser for maximum privacy and security. The tool provides a clean, intuitive interface with real-time validation and beautifully formatted output.

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How to Use

To CREATE a JWT: Enter header parameters as JSON (e.g., {"alg": "HS256", "typ": "JWT"}), payload claims as JSON (e.g., {"sub": "1234567890", "name": "John Doe"}), select an algorithm, and enter a secret key. Click 'Build JWT' to generate the token.
To DECODE a JWT: Paste an existing JWT token into the 'Encoded JWT' field and click 'Decode JWT' to view its header and payload.
Use the 'Clear All' button to reset all fields.
The results section shows the encoded JWT (which you can copy) and the decoded header and payload in formatted JSON.

Frequently Asked Questions

Find Quick Answers

What is a JWT?

JWT (JSON Web Token) is a compact, URL-safe token format used for authentication and information exchange. It consists of three parts: header, payload, and signature, separated by dots.

Which algorithms are supported?

This tool supports HMAC algorithms: HS256, HS384, and HS512. These use a shared secret key for signing and verification.

Is my data secure?

Yes! All JWT encoding and decoding happens entirely in your browser using JavaScript. No data is sent to any server, ensuring complete privacy.

Can I decode any JWT?

You can decode any JWT to view its header and payload (the first two parts). However, signature verification requires the correct secret key and algorithm.

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