Security & Crypto Tools
JWT Decoder
Decode the header and payload of a JSON Web Token.
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What is JWT Decoder?
A JWT decoder that splits a token into header and payload, pretty-prints the JSON, and flags expiry and insecure alg:none tokens.
How it works
The token is split on '.', base64url-decoded, and parsed; expiry is checked against the current time and insecure algorithms are flagged.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.