It Is A War Out There - Take Control of Your Supply Lines with HtDTY
3 points by AndrewStephens
3 points by AndrewStephens
In theory, each user would download $LargeJSLibrary once and cache it, allowing sites A, B, and C to load quicker
Except browsers have to keep a split-brain approach per domain to prevent websites from sniffing out whether you already visited them / another website.
You are right, of course, but this wasn't the case when the idea of serving popular resources from CDNs first arose. Browsers have had to introduce measures to prevent leaking information through side channels because they recognize that third party resources are an attack vector. All the more reason not to bother with CDNs.