Local Cryptography & Privacy

Online JWT Token Inspector

Decode, inspect and audit JSON Web Tokens (JWT) with 100% client-side privacy. Zero data is ever sent across the network.

Zero-knowledge: 100% processed locally on your device
Header • Payload • Signature
HEADER (Algoritmo & Tipo) 
{}
PAYLOAD (Datos & Claims) 
{}
Where to store team credentials?

Discover Medel Vault, our enterprise password manager with zero-knowledge encryption and built-in 2-step verification.

Explore Medel Vault
Frequently Asked Questions

JWT Tokens & Security FAQ

What is a JSON Web Token (JWT) and how is it structured?
A JWT is an open standard (RFC 7519) for transmitting compact, self-contained claims securely as a JSON object. It consists of three parts separated by dots (Header.Payload.Signature), encoded in Base64Url.
Is it safe to paste my tokens into this decoder?
Yes, absolutely. Unlike other online tools that transmit tokens to a remote backend, our inspector runs 100% client-side in your local browser JavaScript engine. No token data or secrets are ever sent across the network.
Why is the "none" algorithm vulnerability so critical?
If an API accepts tokens signed with "alg": "none", an attacker can tamper with user roles or IDs in the Payload and remove the signature. The server may accept the forged token, leading to total account takeover.
Should I store passwords or sensitive data in the Payload?
Never. Standard JWTs are digitally signed but NOT encrypted (they are simply Base64Url-encoded). Anyone in possession of the token can read all claims. Never place passwords, secrets, or financial information inside a JWT payload.
How can my company securely manage JWT signing secrets and API keys?
The industry recommendation is storing cryptographic secrets in a zero-knowledge credential vault. To safeguard API keys and prevent source code leaks, discover Medel Vault, our enterprise password and secret manager.