[pdkl95]

In addition to the (significant) bandwidth savings, this is an important idea for privacy/tracking reasons as well. I may be fine with websites A, B, and C logging that I made a request for one of their pages, but I'd rather not give Google[1] the browsing path A->B->C just because they host jQuery.

While browsers having an internal copy of various common scripts is a great idea, I was briefly working on a Firefox addon that would simply hard-caches any URL that matched some sort of criteria (e.g. regexp for "//ajax.googleapis.com/ajax/libs/.*\.js")

Unfortunately, the project is on hold for now. While it it was easy to match HTTP requests with an observer for 'http-on-modify-request', the nsIHttpChannel[2] object you get from that only seems to let you redirect the request. I considered trying to redirect to a "chrome:" or "file:" url, but that seem like a horrible solution. The real way to mess with HTTP loading and caching, unfortunately, is buried somewhere I have yet to find. :/

[1] or any other shared CDN, such as CloudFlare and their horrible hashed domain names

[2] https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XPCOM/...