Making your website "cross-origin isolated" using COOP and COEP | Articles | web.dev
Some web APIs increase the risk of side-channel attacks like Spectre. To mitigate that risk, browsers offer an opt-in-based isolated environment called cross-origin isolated. Use COOP and COEP to set up such an environment and enable powerful features like `SharedArrayBuffer`, `performance.measureUserAgentSpecificMemory()` or high resolution timer with better precision.
https://web.dev/articles/coop-coep