JWT Builder
Create and sign JSON Web Tokens with custom claims
Note: Signing uses HMAC-SHA256 via Web Crypto API. Your key never leaves your browser.
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How to Use JWT Builder
- Edit the header and payload JSON
- Enter your secret key
- Click Build JWT to generate and sign the token
Frequently Asked Questions
Is my secret key safe in this tool?
Yes. The key never leaves your browser. All JWT signing happens client-side using the Web Crypto API. No data is transmitted to any server.
What signing algorithms are supported?
HS256 (HMAC-SHA256), HS384, and HS512 for symmetric signing. These are the most widely used algorithms for JWTs in web applications and APIs.
Can I set custom claims in the JWT payload?
Yes. Add any custom key-value pairs alongside standard claims like sub (subject), iat (issued at), and exp (expiration). The tool validates JSON syntax as you type.
How do I set an expiration time for the JWT?
Add an "exp" claim with a Unix timestamp value. The tool can help you calculate the timestamp for common durations like 1 hour, 24 hours, or 7 days from now.
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