Years ago, big tech companies stumbled on a brilliant scheme for collecting data on web-users: they started providing incredibly useful free Javascript libraries to web publishers: whenever a web publisher embedded one of these libraries, it would serve as a tracking beacon for everyone who visited that publisher’s site, all without having to get into the messy business of even serving ads.
What’s more, because these libraries were key to laying out and rendering the web-pages you visit, blocking the libraries would render many pages and services unusable, meaning that they were likely to get unblocked by users.
Now, Adblock — a popular adblocking browser extension — has added library caching for the most popular Javascript libraries. Once your browser has downloaded, say, Jquery, it will remain cached, meaning that the next time you encounter a website that calls on that library, you will be able to start rendering the page straightaway, without waiting for a download — and that means that your browser also won’t be loading a version of node.js that is provided free in the hopes of spying on your internet usage.
It’s only available in Adblock’s Chrome extension (for now), and it only caches Jquery (also for now).
AdBlock says it started working on this feature for two reasons. First, by serving files from a local folder it means that sites will load faster. Second, is related to user privacy, and most specifically for JavaScript files loaded from CDNs (Content Delivery Networks).“Many of the most widely-used CDNs are operated by large technology companies, like Google and Microsoft,” AdBlock says. “It is possible that these companies are tracking requests to their CDNs in a way that could be tied back to individual users.”
By keeping copies of popular JavaScript libraries in a local folder, AdBlock prevents this additional tracking behavior.
AdBlock Adds Feature to Cache Popular JavaScript Libraries [Catalin Cimpanu/Bleeping Computer]