https://nalar.dev/tags/coep/ Recent content in COEP on Nalar Hugo en-us Sat, 19 Sep 2026 00:00:00 +0000 https://nalar.dev/coop-and-coep-turn-cross-origin-isolation-into-a-document-group-boundary/ Sat, 19 Sep 2026 00:00:00 +0000 https://nalar.dev/coop-and-coep-turn-cross-origin-isolation-into-a-document-group-boundary/ <h1 id="coop-and-coep-turn-cross-origin-isolation-into-a-document-group-boundary">COOP and COEP Turn Cross-Origin Isolation into a Document-Group Boundary</h1> <p>A web page can be same-origin with its own application code while still maintaining relationships with cross-origin popups, frames, workers, and resources. Those relationships matter when a browser decides which documents can occupy the same browsing context group and which capabilities can be exposed safely.</p> <p>Cross-origin isolation changes that arrangement through two response policies with different jobs. <code>Cross-Origin-Opener-Policy</code> (COOP) controls top-level opener relationships and browsing context group switches. <code>Cross-Origin-Embedder-Policy</code> (COEP) constrains the cross-origin resources a document and its descendants may load. Used together in the configuration required for isolation, they establish a browser-enforced boundary that is broader than the same-origin policy alone.</p>