[tofflos]

The cache used to be shared between domains but that's no longer the case due to privacy concerns and limited effectiveness.

> As of Firefox v85 and Chrome v86 the browser cache will be partitioned, this means that the same resource included on two sites will have to be downloaded from the internet twice and cached separately.

Source https://www.peakhour.io/blog/cache-partitioning-firefox-chro....

[acdha]

This still helps other requests to the same origin, which is a very common situation if you don’t have the extra resources needed to get an SPA up to the same performance and reliability levels.