Firefox version 85, set to ship to users in January, will bring a new anti-tracking feature called storage (or cache) partitioning, which should help protect users from websites that try to track their data.
The new feature is based on the ‘Client-Side Storage Partitioning‘ standard being developed by the World Wide Web Consortium’s Privacy Community Group, according to ZDNet. While storage partitioning can be highly technical, at a basic level it works by separating data saved to your computer by websites into different segments.
Over the last few months, cookies were the focus of anti-tracking privacy measures. Designed as a method for websites to store small pieces of important information on users’ computers, such as login activity or items in an online cart, cookies became a tool for web-based apps and services to track users. However, cookies are just one of many storage mediums websites can use to track users.
Storage partitioning steps in here to make it harder for websites and other third-party entities, such as ad and analytics companies, to track users by isolating data on a per-website basis. Currently, data and resources like cache, favicons, CSS files and more are saved in a singular pool of data accessible to any website. By partitioning these resources based on websites, it could prevent companies from tracking users through this data.
Mozilla will partition the following data in Firefox 85:
- HTTP cache
- Image cache
- Favicon cache
- Connection pooling
- StyleSheet cache
- HTTP authentication
- Speculative connections
- Font cache
- Intermediate CA cache
- TLS client certificates
- TLS session identifiers
- CORS-preflight cache
Firefox will implement a wider partitioning system than others
Several other browsers have implemented variations of this data partitioning, although ZDNet reports that Firefox’s implementation will cover more data than others.
Apple’s Safari was the first to implement data partitioning in 2013 when it began partitioning the HTTP cache. Later, when the company introduced its Tracking Prevention feature, it partitioned more data.
Google added HTTP cache partitioning to Chrome in version 86 as well, but noted some performance issues. For example, Google Fonts lost performance since it could no longer store fonts in the shared HTTP cache.
ZDNet says the Mozilla team expects Firefox will also see performance issues for some sites after implementing storage partitioning. However, it feels the hit to performance is worth it for the privacy and security benefits. Further, storage partitioning may have a side benefit of blocking ‘supercookies,’ a type of browser cookie that abuses shared storage mediums to track users across the web.
Update 12/23/2020 at 1:09pm: Corrected the new feature from the incorrectly reported network partitioning name to its proper storage partitioning name.