nested chains · chrome

Which part of the chain ends up in the key

Pick which document in the chain requests https://x.example/lib.js.

a.example top-level
b.example iframe
c.example nested iframe

Resulting cache key

Chrome · triple key (https://a.example, https://a.example, https://x.example/lib.js)
Firefox and Safari · double key (https://a.example, https://x.example/lib.js)

The request comes from the top-level document itself, so top-level site and frame site are the same.

This is a simulation. There are no real iframes and no network requests: the keys are built by applying each engine's documented model.