Say Goodbye to Resource-Caching Across Sites and Domains

If everybody loads the same script file (eg: cdn.jquery.com/jquery.latest.js – or whatever URL), then the script file would be cached by the browsers, and other sites requesting the same script would benefit from the speedup of already cached resources. Users would have popular libraries like jQuery already sitting in their browser cache because earlier visited sites requested them.

All this worked great, but as it is with many great inventions in web technology, cross-site resource caching enabled new ways to track users across different sites.

Webkit (Safari) changed its caching strategy already in 2013 to prevent user tracking via the browser cache. Starting with v86, Chrome will be using combined cache keys. This change means that it’s time to say goodbye to third-party resource-sharing across the web. With Chrome’s market share of roughly 70%, most browsers hitting our sites will use partitioned browser caches from now on.

What does this change mean for you? If your sites live on modern hosting that provides a CDN and supports HTTP/2, you can drop the third-parties and should ship all resources yourself. Relying on a third-party provides little value in 2020.