Enlarge / Breaking the browser cache up into separate pools prevents sophisticated timing probes that let one site know whether you're logged into another. (credit: Mozilla / Jim Salter )

Firefox version 85 will be released in January 2021, and one of its features is increased user privacy via improvements in client-side storage (cache) partitioning . This has been widely and incorrectly reported elsewhere as network partitioning, likely due to confusion around the privacy.partition.network_state flag in Firefox, which allows advanced users to enable or disable cache partitioning as desired.

What is cache partitioning—and why might I want it?

In a nutshell, cache partitioning is the process of keeping separate cache pools for separate websites, based on the site requesting the resources loaded, rather than simply on the site providing the resources.

With a traditional, globally scoped browser cache, you might see behavior like this: