Thread:Project:Support desk/Why mediawiki load JS before entire page ?/reply

You don't. jQuery and MediaWiki-JS is loaded before the rest of the page because it is used in all modules (including modules that are used from the top-queue). All other code is either loaded from the bottom of the page (after render) or asynchronously while the page is rendering. This balance is for the best performance.

Web page testers only give you theoretical advice (some testers are better than others). MediaWiki is not a simple web page engine but a rather feature-rich one. It is optimized already and high-end performance (All Wikipedias and their sister projects runs on it!). It is more complex and beyond the static analysis that WebPagetest can do.

The general advice of loading things after page render is good and MediaWiki is doing that, just not for jQuery (and that is a good thing).