Defaults.Exposed › September 2026 census › v10 registry › Content-Security-Policy
Content-Security-Policy
Methodology v10 · canonical ID csp-header · Web Security · scored · census as of September 5, 2026
Reduces the chance a hacked or injected script steals customer data off your site.
Definition
| Canonical ID | csp-header |
|---|---|
| Category | Web Security |
| Grade impact | Scored, counts toward the grade |
| Pass | The site sends an effective Content-Security-Policy header. |
| Fail | No CSP header is sent. |
| Example (passing) | Content-Security-Policy: default-src 'self' |
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
10.1% of domains whose page returned a 2xx response send an effective Content-Security-Policy header (12,734,849 of 125,815,036, as of September 5, 2026).
The four response-header checks are evaluated only where the page answered directly with a 2xx status; redirects, errors and unanswered fetches return N/A and are never counted as a failure, so this denominator is smaller than the graded population and the share of all graded domains is lower.
Census denominator: 316,600,902 graded domains; this check is measured only against domains whose page returned a 2xx response (125,815,036). 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/csp
Cite this check
Defaults.Exposed, "Content-Security-Policy (csp-header)", Grading Methodology v10 (census as of September 5, 2026). https://defaults.exposed/methodology/csp-header
Permalink: https://defaults.exposed/methodology/csp-header ·
All 34 checks: v10 registry ·
Machine-readable: /methodology/checks.json ·
Licence: open data