JWT Expiry Checker

This tool checks whether a JSON Web Token has expired and shows its key timing claims, so you can quickly tell if a token is still valid. JSON Web Tokens, or JWTs, are the standard way modern applications carry identity and authorisation between a server and a client. A token is only meant to be valid for a limited time, and its payload carries timing claims that control this: the expiry time, the issued-at time, and sometimes a not-before time. When an API call fails with an authorisation error, one of the first things to check is whether the token has simply expired, but reading the raw Unix timestamps in a token is awkward. This tool does it for you. You paste a token, and the calculator decodes its payload, reads the expiry, issued-at and not-before claims, converts those Unix timestamps into readable dates, tells you whether the token is currently expired or still valid, and shows how long until it expires or how long ago it did. The result updates as you paste, and everything runs in your browser, so the token is never uploaded, which matters because tokens grant access. Use it to debug authentication problems, to check a token's validity, or to read its timing. The expiry claim, exp, is the moment after which the token should be rejected; the issued-at claim, iat, records when it was created; and the not-before claim, nbf, is the moment before which it is not yet valid. The check compares the current time on your device against these claims. Two important caveats: this reads the claims but does not verify the token's signature, so a token shown as valid is not necessarily authentic, only unexpired; and the times depend on your device clock, so a badly set clock will affect the result. If a token has no expiry claim, it does not expire by time, which the tool will indicate.

Reads the exp, iat and nbf claims and compares with your device clock. Does NOT verify the signature, so 'valid' means unexpired, not authentic. Times use your local clock.