JWT Encoder
Create a signed HS256 JSON Web Token from a JSON payload and secret.
Testing an API that expects a JWT, debugging an authentication flow, or just understanding how a token's signature is derived from its header and payload often calls for generating a real, correctly-signed token rather than just decoding an existing one.
This tool builds a standards-compliant JWT using the HS256 (HMAC-SHA256) signing algorithm, the most common symmetric-key JWT signing method — you provide the payload as JSON and a secret key, and it produces the complete three-part token (header, payload, and signature) exactly as a real authentication server would. The implementation matches the JWT specification precisely, verified against the standard reference example published on jwt.io.
All signing happens using the Web Crypto API's HMAC implementation directly in your browser, so your secret key is never transmitted anywhere — important since a JWT secret is exactly the kind of value that shouldn't be sent to a third-party server.
How to use JWT Encoder
- 1
Enter your payload
Type the claims you want in the token as JSON.
- 2
Enter your secret
Type the HMAC secret key used to sign the token.
- 3
Copy the signed token
The complete JWT updates live and can be copied instantly.
Features
- HS256 (HMAC-SHA256) signing, matching the JWT specification exactly
- Secret key never leaves your browser
- Live encoding as you edit the payload or secret
- Verified against the standard jwt.io reference example
Frequently asked questions
Common mistakes to avoid
- Entering payload JSON with a trailing comma or syntax error, which will fail to encode.
- Assuming the signature alone makes the payload confidential — JWT payloads are only encoded, not encrypted, and remain readable by anyone with the token.
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