JWT decoder.

A JSON Web Token is three Base64url strings joined by dots: a header naming the algorithm, a payload of claims (who, for whom, until when) and a signature over the first two. Anyone can read the first two; only the key can check the third.

Decoding is reading the header and payload, which are encoded, not encrypted. Verifying is recomputing the signature with the issuer's secret (HS256) or checking it with their public key (RS256, ES256, EdDSA). A decoded token proves nothing until it is verified.

That the header and payload are exactly what the key holder signed: change one character and verification fails. It does not hide anything (the payload is readable by anyone), and it does not stop a stolen token from being replayed until it expires.

exp (expiry) and nbf (not before) are compared with your clock and written as dates with how long ago or how soon; iat (issued at) is flagged if it is in the future. A token without exp never lapses, and alg none is marked as unsigned.

Registered claim names: iss is the issuer, sub the subject (usually a user id), aud the audience the token is meant for, jti a unique token id. The claims table names these and the common ones such as scope, azp, email and roles.

Paste the token, with or without a leading Bearer. The header and payload appear as formatted JSON, the time claims as dates, and the checks say what passes and what fails.

Paste the secret for HS256, HS384 or HS512 (as text, Base64url or hex), or the public key for RS, PS, ES or EdDSA tokens as a PEM, a JWK or a whole JWKS, where the key is picked by the token's kid. The verdict appears at once.

No. The decoding and the signature check run in your browser with the Web Crypto API, and the page makes no request with the token or the key. It is still wise to paste production secrets only on a machine you trust.

No. The JWT decoder is free and opens without a sign-in, an account or an install.

Nothing. The JWT decoder holds your input in the page's memory, so closing or reloading the tab clears it, and it saves nothing in this browser.

Yes, the Bearer word is dropped before the token is read, so a whole Authorization header value can be pasted as it is.

No: it expects exactly three Base64url parts separated by dots, and says how many it found. An encrypted token (JWE) has five parts and can't be read without the key anyway.

It flags a header with alg set to none as a token without a signature that anyone could have written. For any other algorithm it names the algorithm and says the signature can only be checked with the key.

The header, the payload and the signature are shown as separate parts, and the signature has its own copy button. It stays in the third part's Base64url form, since reading it needs the key.

Closest to the JWT decoder: JWT encoder, Base64 decoder, Unix timestamp converter, RSA key generator. Each opens on its own page, free and in the browser.

The JWT decoder is one of 20 in its group. The group's page, /tools/security, lists them all.

The tool is free. Its interface is built from shadcn.io's own components (Button, Input, Slider and the rest of the registry under /ui), which come in React, Vue, Svelte and Solid. Pro adds the blocks and templates for the product around it.