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HSTS Header Builder and Inspector
Build or inspect a bounded Strict-Transport-Security field.
Entered directives, Pasted bare header value
strict-transport-security.txt, hsts-report.json
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
This tool needs JavaScript. If it does not load, refresh the page and try again.
How to use this tool
- Enter the shown fields and choose the stated mode or options.
- Build or inspect HSTS and inspect the complete result.
- Download strict-transport-security.txt, hsts-report.json.
Examples
max-age=31536000; includeSubDomains produces a local one-year directive check.
Limitations
- Local syntax and directive checks only; TLS, redirects, preload registration and browser persistence are not verified.
- The local max-age cap is 63,072,000 seconds. Parse accepts at most 100 unique directive names and requires one max-age.
- Known flags must be valueless. Unknown valid extensions are retained with diagnostics rather than interpreted as policy.
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