The HTTP Cross-Origin-Opener-Policy (COOP) response header allows you to ensure a top-level document does not share a browsing context group with cross-origin documents.| MDN Web Docs
This article lists the most important security headers you can use to protect your website. Use it to understand web-based security features, learn how to implement them on your website, and as a reference for when you need a reminder.| web.dev
HTML Design Principles| www.w3.org