JWT Decoder & Visualizer

JSON Web Tokens (JWTs) are the backbone of modern authentication and authorization pipelines. This tool decodes any Base64URL-encoded JWT directly in your browser — no network requests, no server-side processing, complete privacy.

JWT Structure

A valid JWT is composed of three Base64URL-encoded segments separated by dots (header.payload.signature):

• Header — Specifies the signing algorithm (e.g., HS256) and token type.
• Payload — Contains claims such as sub, iat, exp, and custom fields.
• Signature — A cryptographic hash that verifies the token has not been tampered with.

Token Expiry (exp claim)

The exp claim is a Unix timestamp representing when the token expires. This tool automatically computes the expiry status and displays whether the token is still active or has expired.

All decoding is performed entirely client-side using the Web Crypto API. Your token never leaves your browser.