I think it would actually make more sense for the sha256 to be in the headers for setting it. It seems a bit weird for a property on a link tag pointing at a fi

I think it would actually make more sense for the sha256 to be in the headers for setting it. It seems a bit weird for a property on a link tag pointing at a file to determine what we think the hash of that file is (not to mention quite un-fun to maintain). Of course, that means without duplicating it you would still need a request similar to If-Modified-Since - something like If-Hash-Differs: <sha256 hash>, but still better than downloading the whole file. I've thought about this exact problem before and one nice way to solve it would be through some kind of signing process - so you instead tell the browser "I need com.jquery.1.7.2" and there would be some way of verifying that a given instance of that file was legitimate, and could thus be cached across multiple URIs.