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UX Tip #68 JS/CSS optimisation – concatenation


An optimised technical solution increases performance and enhances User Experience. It may not seem like it, especially for static content such as JS/CSS, but server requests are costly. There is a fair bit of overhead in each server request, a traditional HTTP/1 page load looks like the following: DNS lookup Establish connection to the web server Send HTTP request Wait for response Receive response Steps 1-3, in an average page load, are generally fairly small and are usually a few hundred milliseconds. However, if you have 30-40 JS/CSS files per page, those milliseconds can add up very quickly.

So, it is a good idea to concatenate your JavaScript or CSS asset files is to reduce the number of server requests that a browser needs to do.