JWT Encoder/Decoder

A JWT (JSON Web Token) is a compact format for transmitting signed data, made of three dot-separated parts: a header, a payload, and a signature. This tool decodes any JWT and shows all three parts, and can also build a new token signed with HMAC.

Decoding does not verify the signature — reading a token's contents needs no secret key. Verifying the signature only matters when you need to trust the token as genuine.

How to use it

• Decode: paste a JWT and the tool splits it into header, payload, and signature, highlighting standard claims like exp, iat, and sub.
• Encode: fill in the header and payload, provide a secret, and get a signed HMAC token (HS256/HS384/HS512) back.
• Check expiry: the exp claim is shown as a normal date, so you can immediately tell if a token has expired.

Common uses

• Debugging authentication issues by inspecting exactly what a request's token contains.
• Checking which claims (roles, permissions, expiry) your backend issues.
• Generating a test token for local development without running an auth server.

Things to keep in mind

A JWT is not encrypted, only Base64URL-encoded — anyone can read the payload. Never put passwords or other secrets in it.

The signature protects against tampering, not against being read. For confidentiality you need extra encryption (JWE) or an HTTPS transport.