Double-keyed Caching: How Browser Cache Partitioning Changed the Web
January 13, 2025
The web’s caching model served us well for over two decades. Recently, in the name of privacy, it’s undergone a fundamental shift that challenges many of our performance optimization assumptions. This is called Double-keyed Caching or cache-partitioning more generally. Here’s what changed, why it matters, and how to adapt.
Source: Double-keyed Caching: How Browser Cache Partitioning Changed the Web
One aspect of browser caching that has changed in recent years is a move to cache partitioning. Traditionally a browser would cache a resource like a JS library, and then regardless of what domain used that resource, that cached version was used. Now the same resource will be ached on a per-domain basis. Which has implications for privacy, security and performance that Addy Osmani explores here.
