About this tool
JWT Builder — Build and sign JSON Web Tokens with HS256/HS512. Free, fast and private. Runs entirely in your browser at Quick Calci Tools.
Examples
Common scenarios for the JWT Builder.
Dev session claim
- alg
- HS256
- exp
- true
Signed JWT with exp minutes ahead for API mocks.
Longer HMAC
- alg
- HS512
Stronger hash for parity with hardened services.
Who uses the JWT Builder?
Common scenarios and audiences for this tool.
Backend devs
Reproduce gateway auth locally without waiting for IdP uptime.
QA engineers
Mint expired or future tokens for negative-path tests.
Students
See how base64url segments concatenate before signature.
Mobile devs
Stub GraphQL authorization headers during UI work.
Pen testers
Craft tampered claims in isolated lab environments ethically.
Frequently asked questions
Everything you need to know about the JWT Builder.