ShadowToolkit

JWT Encoder

Encode and sign JSON Web Tokens (JWT) with HMAC secret keys locally.

100% In-Browser

JWT Encoder & Decoder

100% In-Browser PrivacyLocal

Your files and data are processed locally and never leave your device.

What is JWT Encoder?

JWT Encoder creates and cryptographically signs JSON Web Tokens (RFC 7519) directly inside your web browser. Customize header claims, payload data (iss, sub, exp, custom claims), and sign tokens with secret keys using the native Web Cryptography API.

Zero-Server Client-Side Guarantee

Unlike legacy online utilities that upload sensitive media and documents to remote cloud storage, Shadow Toolkit executes this entire operation directly within your browser's local runtime. Your raw data never crosses the network.

Key Capabilities

  • Cryptographically signs JWTs using HMAC-SHA256 (HS256) via the Web Crypto API
  • Configurable standard claims: iss, sub, aud, exp, nbf, and custom JSON properties
  • Auto-calculates Unix timestamps for token expiration (exp) and issued-at (iat)
  • Real-time Base64URL encoding for Header, Payload, and Signature segments
  • 100% private in-browser signing—your secret signing key never leaves your device

Common Use Cases

1Generating mock JWT bearer tokens for local API development and unit testing
2Prototyping authentication flows and microservice authorization headers
3Testing token expiration and claims validation in backend authentication middlewares
4Accelerating daily software development workflows, API debugging, and frontend data modeling

How to use JWT Encoder

01

Edit Header & Payload

Customize your JSON header and payload claims (e.g. user ID, roles, exp).

02

Enter Secret Key

Provide your signing secret key for the HMAC-SHA256 algorithm.

03

Copy Signed JWT

Click 'Copy Token' to use the signed bearer token in Postman, curl, or your frontend.

04

Integrate with Project

Click 'Copy to Clipboard' or download the file to integrate the verified JWT Encoder output directly into your application codebase or API client.

Frequently Asked Questions

Yes! Unlike other JWT websites that send keys to cloud servers, Shadow Toolkit computes HMAC signatures using your browser's native Web Cryptography API. Your secret key never crosses the network.

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