Is my data sent to a server?

No. This tool runs entirely in your browser. Your data never leaves your browser.

Does this validate the JWT signature?

No. It only Base64URL-decodes the header and payload so you can inspect claims. Use your server and the issuer’s keys to verify signatures.

No — decoding happens locally in this tab. Do not paste production secrets into shared machines.

A JWT has three parts separated by dots: header.payload.signature. Make sure you pasted the full token including all segments.

Developer Tools

Is my data sent to a server?: No. This tool runs entirely in your browser. Your data never leaves your browser.
Does this validate the JWT signature?: No. It only Base64URL-decodes the header and payload so you can inspect claims. Use your server and the issuer’s keys to verify signatures.
Is my token sent to a server?: No — decoding happens locally in this tab. Do not paste production secrets into shared machines.
Why do I see “3 segments” errors?: A JWT has three parts separated by dots: header.payload.signature. Make sure you pasted the full token including all segments.

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