CODEWITHSUNDEEP
performancecachingoptimizationbrowsercdn
Joseph
Joseph

Reputation: 119887

Do websites share cached files?

We're currently doing optimizations to our web project when our lead told us to push the use of CDNs for external libraries as opposed to including them into a compile+compress process and shipping them off a cache-enabled nginx setup.

His assumption is that if the user has visits example.com which uses a CDN'ed version of jQuery, the jQuery is cached that time. If the user happens to visit example2.com and happen to use the same CDN'ed jQuery, the jQuery will be loaded from cache instead of over the network.

So my question is: Do domains actually share their cache?

I argued that even if it is possible the browser does share cache, the problem is that we are running on the assumption that the previous sites use the same exact CDN'ed file from the same exact CDN. What are the chances of running into a user browsing through a site using the same CDN'ed file? He said to use the largest CDN to increase chances.

So the follow-up question would be: If the browser does share cache, is it worth the hassle to optimize based on his assumption?

I have looked up topics about CDNs and I have found nothing about this "shared domain cache" or CDNs being used this way.

Upvotes: 2

Views: 68

Answers (1)

Tom Tom
Tom Tom

Reputation: 3698

Well your lead is right this is basic HTTP. All you are doing is indicating to the client where it can find the file. The client then handles sending a request to the CDN in compliance with their caching rules.

But you shouldn't over-use CDNs for libraries either, keep in mind that if you need a specific version of the library, especially older ones, you won't be likely to get much cache hits because of version fragmentation. For widely used and heavy libraries like jQuery you want the latest version of it is recommended.

If you can take them all from the same CDN all the better (ie: Google's) especially as http2 is coming.

Additionally they save you bandwidth, which can amount to a lot when you have high loads of traffic, and can reduce the load time for users far from your server (Google's is great for this).

Upvotes: 2

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