What is the "Missing COOP header" check?

P3 · LowSecurity

Missing COOP header

No Cross-Origin-Opener-Policy

Code: missing_coop

Why it matters

No Cross-Origin-Opener-Policy. Browsers and users expect sites to be secure. Missing protections expose visitors to data theft, phishing, and loss of trust.

Related checks in Security

SSL certificate expired

HTTPS certificate has expired

Certificate expiring soon

Certificate expires in < 7 days

Certificate expiring

Certificate expires in < 30 days

No HTTPS redirect

HTTP does not redirect to HTTPS

Mixed content

HTTPS page loads HTTP resources

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