JWT Encoder

Create a signed JSON Web Token from a JSON payload using HS256, HS384 or HS512.

What is the JWT Encoder?

Signing a JWT lets a server verify later that the claims were not altered.

How does it work?

The header and payload are serialised, Base64URL-encoded and joined with a dot. An HMAC of that string with your secret becomes the signature.

Formula

signature = HMAC-SHA256(secret, base64url(header) + "." + base64url(payload))

Example

A payload with sub, role, iat and exp signed with HS256 produces a three-part token you can test in the JWT Decoder.

Frequently asked questions

Is my data sent to a server?

No. This tool runs entirely in your browser; nothing you paste is uploaded or stored.

Why not RS256?

RS256 needs a private key. Asymmetric signing is best done on your server; this tool focuses on HMAC for testing.

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