Website Security Header Checker
Mozilla Observatory-grade scoring for HTTP headers and TLS — instant, free
Test any public website's HTTP security posture in seconds. SentinelOSS checks for Content Security Policy, HTTP Strict Transport Security, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, and Permissions-Policy — then grades your site A through F based on Mozilla Observatory standards. TLS certificate validity and HTTPS redirect are checked automatically.
How to use
- 1Enter any public URL (e.g. https://example.com). The site must be publicly reachable.
- 2SentinelOSS sends a request and inspects all security-relevant HTTP response headers.
- 3Each header is rated pass, warn, or fail with a plain-English explanation and a recommended fix.
- 4Your site gets an overall score (0–100) and letter grade — share the results with your team or clients.
Code & dependencies
What you installMachines
What you run it onWeb & domain
What you exposeSupply chain & AI
What you inherit🌐Website~5–15 secondsReads: response headers and cookie flags on the URL you give us
Enter any public website URL. SentinelOSS checks HTTP security headers, TLS certificate validity, and HTTPS configuration using Mozilla Observatory.
Try:
What we check
- ✓ Content Security Policy
- ✓ Strict Transport Security
- ✓ X-Frame-Options
- ✓ X-Content-Type-Options
- ✓ Referrer Policy
- ✓ Cookie Security flags
- ✓ TLS certificate validity
- ✓ HTTPS redirect (HTTP→HTTPS)