JWT Decoder Online — Inspect JSON Web Tokens Instantly

JWT Decoder Online A JWT decoder online tool lets you inspect any JSON Web Token instantly — no library, no terminal, no code. Just paste the token and see the decoded header, payload, claims, and expiry time in a readable format. This guide covers how JWTs work, what each part contains, and how to decode them in code when you need to do it programmatically. What Is a JWT? A JSON Web Token (JWT) is a compact, self-contained token used for authentication and information exchange. It is the standard format for OAuth 2.0 access tokens, OpenID Connect ID tokens, and custom auth systems. A JWT has three parts separated by dots: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjEyMywicm9sZSI6ImFkbWluIiwiZXhwIjoxNzQzMDAwMDAwfQ.abc123signature Each part is Base64url-encoded: Header — algorithm and token type Payload — the claims (user data, expiry, issuer, etc.) Signature — cryptographic proof the token was not tampered with Decoding the Three Parts Header Decoding the first segment: { "alg":