Defaults.Exposed › September 2026 census › v10 registry › HSTS
HSTS
Methodology v10 · canonical ID hsts-header · Web Security · scored · census as of September 5, 2026
Forces the secure padlock every visit so customers can't be downgraded to an insecure connection.
Definition
| Canonical ID | hsts-header |
|---|---|
| Category | Web Security |
| Grade impact | Scored, counts toward the grade |
| Pass | The site sends a Strict-Transport-Security header with a meaningful max-age. |
| Fail | No HSTS header is sent over HTTPS. |
| Example (passing) | Strict-Transport-Security: max-age=31536000; includeSubDomains |
No-data rule: when this check couldn't be determined for a domain (timeout, SERVFAIL, redacted source) it returns N/A and is excluded from that domain's scoring denominator: "couldn't determine" is never counted as a failure. "Determined absent" is a real fail.
Prevalence across the census
21.1% of HTTPS-serving domains send an HSTS header (44,684,372 of 212,154,494, as of September 5, 2026).
Census denominator: 316,600,902 graded domains; this check is measured only against HTTPS-serving domains (212,154,494). Aggregates only: never an individual domain's result.
Fix it
Plain-English impact, cost of ignoring it, and step-by-step remediation: defaults.exposed/fix/hsts
Cite this check
Defaults.Exposed, "HSTS (hsts-header)", Grading Methodology v10 (census as of September 5, 2026). https://defaults.exposed/methodology/hsts-header
Permalink: https://defaults.exposed/methodology/hsts-header ·
All 34 checks: v10 registry ·
Machine-readable: /methodology/checks.json ·
Licence: open data