You didn't get my point, probably because of my terrible english :) The browser has no way of knowing in advance if a script doesn't depend on any of the previous ones, so it cannot optimize this specific case and parse/execute the script before the other ones have been executed. You can manually tell the browser to load the scripts and execute them as soon as they're ready, in no particular order, via the async attribute. If you don't, the browser is going to assume that the order is important and load them one by one.