Firefox 85 introduces “client-side storage partitioning.” Modern web browsers heavily rely on caching content to offer a fast browsing experience. However, shady websites can misuse caching mechanisms to identify and track users.
The “client-side storage partitioning” (aka “network partitioning” or “cache partitioning”) isolates the cache belonging to website A from the cache belonging to website B. The isolation ensures that B can’t query for cached content of A to see whether the user visited website A before. Apple’s Safari and Google’s Chromium already partially partition their caches.
In Firefox 84, you can already enable the “client-side storage partitioning.” Go to about:config, and set “privacy.partition.network_state” to True. While the isolation of these resources can improve your tracking resistance, it might negatively impact your web browser’s browsing performance.
Firefox 85 partitions the following network resources:
- Connection pooling
- CORS-preflight cache
- Favicon cache
- Font cache
- HSTS (HTTP Strict Transport Security)
- HTTP authentication
- HTTP cache
- Image cache
- Intermediate CA cache
- OCSP (Online Certificate Status Protocol)
- Speculative connections
- StyleSheet cache
- TLS client certificates
- TLS session identifiers
On a final note, keep in mind that most “privacy checks” don’t check these client-side states. Therefore, even if a check says that websites can’t easily track your web browser, the actual tracking websites might be able to track you if they evaluate these unique states.