Security4 min readSeptember 16, 2026🕒 Updated
JWT Token Decoder Guide — Inspect JSON Web Tokens Safely
Decode JWTs safely in your browser. Learn what makes up a JSON Web Token and why you should never paste them into server-side decoders.
What is a JWT?
A JSON Web Token (JWT) is a standard used to securely transmit information between parties as a JSON object. It consists of three parts: Header, Payload, and Signature.
The Security Risk of Online Decoders
Many online JWT decoders send your token to a backend server to decode it. This is highly dangerous, as JWTs often contain sensitive session data or PII (Personally Identifiable Information).
Our JWT Decoder uses pure client-side JavaScript to base64-decode the header and payload. Your token NEVER leaves your machine.