JWT Decoder
Decode and inspect JSON Web Tokens instantly. View header, payload, and claims with human-readable explanations.
Security notice: Never paste production tokens containing sensitive data into any third-party tool. This decoder runs entirely in your browser — no data is transmitted.
Understanding JSON Web Tokens
JSON Web Tokens (JWTs) are the backbone of modern authentication. Used by APIs, single-page applications, and mobile apps, they securely transmit identity and authorization data between services.
Our JWT Decoder lets you instantly inspect any JWT — see the signing algorithm, read all claims with human-readable explanations, check if the token is expired, and copy individual sections. All processing happens in your browser for maximum security.
Why Developers Love This Tool
Claim Explanations
Hover over any standard claim (iss, sub, exp, iat) to see what it means — perfect for learning JWT structure.
Expiration Status
See "Expires in 2h 15m" or "Expired 3 days ago" at a glance — no manual Unix timestamp conversion.
100% Client-Side
Your tokens never leave your browser. Zero API calls, zero server logging — complete privacy.
JWT Structure Explained
Header
Algorithm & Type
Payload
Claims & Data
Signature
Verification
Common JWT Claims
| Claim | Name | Description |
|---|---|---|
| iss | Issuer | Who created the token |
| sub | Subject | Who the token is about (user ID) |
| aud | Audience | Who the token is intended for |
| exp | Expiration | When the token expires (Unix time) |
| iat | Issued At | When the token was created |
| jti | JWT ID | Unique identifier for the token |