Firefox 85 introduces 'Network Partitioning' for improved tracking resistance

Firefox 85 introduces “Network Partitioning,” which is part of the “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.

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The “client-side storage partitioning” (aka “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 “Network 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:

  • Alt-Svc
  • Connection pooling
  • CORS-preflight cache
  • DNS
  • Favicon cache
  • Font cache
  • HSTS (HTTP Strict Transport Security)
  • HTTP authentication
  • HTTP cache
  • Image cache
  • Intermediate CA cache
  • OCSP (Online Certificate Status Protocol)
  • Preconnect
  • Prefetch
  • Speculative connections
  • StyleSheet cache
  • TLS client certificates
  • TLS session identifiers
This list is only a subset of client-side states in modern web browsers. Go to the "Client-Side Storage Partitioning" website below to see further client-side states that websites can misuse for tracking.

The successor Firefox 86 implements another subset of “client-side storage partitioning,” called “Dynamic State Partitioning.”

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.

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