Double-Keyed Caching: How Browser Cache Partitioning Reshaped the Web

To enhance privacy, browser caching has shifted from a simple key-value store to double-keyed caching (or cache partitioning). This fundamentally changes how resources are cached: previously shared across sites via public CDNs, now each site maintains its own copy. While bolstering privacy by preventing cache probing, timing attacks, etc., this leads to lower cache hit rates and increased network load. The article analyzes this impact on various resources (shared libraries, fonts, large models), proposing solutions like domain consolidation, module federation, and smart resource loading. The era of shared public CDNs may be ending, but the web's adaptability will prevail.