JWT Decoder

Giới thiệu về JWT Decoder

JSON Web Tokens (JWTs) are a compact, URL-safe standard for transmitting signed claims between parties, defined in RFC 7519. A JWT consists of three Base64URL-encoded parts separated by dots: the header (algorithm and token type), the payload (claims such as user ID, roles, and expiration time), and the signature. They are widely used in authentication flows — an API server issues a JWT after login, and the client includes it in every subsequent request so the server can verify identity without querying a database. This decoder lets you instantly inspect any JWT's contents. Paste a token and the tool decodes and pretty-prints the header and payload as formatted JSON, so you can read all the claims at a glance. Timestamp claims (exp, iat, nbf) are automatically rendered as human-readable dates, and expired tokens are flagged in red. Importantly, this tool never sends your token to any server — everything is decoded locally in your browser. Signature verification is intentionally not performed, keeping the tool simple and safe for inspecting tokens without needing a secret key.

Làm sao để JWT Decoder?

1. Paste your JWT (starting with "eyJ...") into the text area at the top of the tool.
2. The header and payload are decoded and displayed as formatted JSON automatically.
3. Check the coloured badges near the top for expiration (exp), issued-at (iat), and not-before (nbf) times.
4. A red "Expired" badge indicates the token's exp claim is in the past.
5. Use the Copy buttons to copy the header or payload JSON to your clipboard.
6. Inspect claim fields such as sub (subject/user ID), iss (issuer), and aud (audience) in the payload section.

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