This complete, single-file solution provides a high-end, professional security workspace. It handles JWT encoding/decoding, JSON validation, and vulnerability simulation entirely in memory using pure JavaScript, CSS, and HTML. ```html Free JWT "alg": "none" Vulnerability Tester & Security Tool

JWT "alg": "none" Vulnerability Tester

A security education tool to simulate and visualize JSON Web Token vulnerabilities.

Header JSON

Payload JSON

Security Context

The "alg": "none" vulnerability occurs when a server accepts tokens without verifying the signature. By setting the algorithm to "none", attackers can bypass signature verification entirely.

Live Token Visualization

Full Encoded String

System Ready