JWT Generator

Generate JSON Web Tokens (JWT). Configure the Header, Payload, and sign with a secret key.

Header

Payload

Keep your secret key safe. Never expose it publicly.

JWT Structure

  • Header: Contains the algorithm and token type information
  • Payload: Contains claims (user data, expiration, etc.)
  • Signature: Generated from Header + Payload + Secret

JWT Generator Guide

Understanding JWT Generation

JWT (JSON Web Token) generation is the process of creating a signed token for user authentication or data exchange. By combining a Header (algorithm, type), Payload (claims data), and Secret Key, you produce a valid JWT. Generated tokens are used across API authentication, session management, Single Sign-On (SSO), and microservice-to-microservice communication. When testing authenticated API endpoints with Postman or cURL, you need a valid JWT, and this tool lets you create one instantly with custom claims and expiration without running a server. It also helps when demonstrating a specific token structure to team members or prototyping JWT-based authentication systems from scratch.

The Mechanism

The JWT Generator constructs three parts (Header, Payload, Signature) step by step based on your input. The Header contains the selected algorithm (HS256/384/512) and token type (JWT) in JSON format. The Payload includes registered claims like sub, iss, and aud alongside any custom claims you define. Time-based values such as exp (expiration) and iat (issued at) are automatically calculated as Unix timestamps relative to the current time. Both the Header and Payload are serialized to JSON strings and then Base64URL-encoded. The Signature is generated by joining the encoded Header and Payload with a dot (.), then applying the HMAC function from the Web Crypto API using your secret key. The final token is formed by concatenating all three parts with dots (xxxxx.yyyyy.zzzzz). Random secret key generation uses crypto.getRandomValues() to produce 256 bits (32 bytes) of cryptographically secure random data.

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