Checks

Cross-Origin-Embedder-Policy (COEP) is present

The response includes Cross-Origin-Embedder-Policy.

Why it matters

COEP is what lets a page require every subresource to opt into being loaded cross-origin.

What to do

require-corp is only useful together with COOP if you need cross-origin isolation.

Reference

Security response headers reduce XSS, clickjacking, and protocol downgrade risk.

OWASP Secure Headers Project