Particularly if It’s Render Blocking – like jQuery
jQuery is such a widely used library, that it’s best to load it first in your site – even if it’s “render-blocking”. There are simply too many plugins in WordPress that rely on jQuery for it to not be available to any inline script. As a result, most WordPress sites load jQuery in render-blocking mode, which slows things down as the browser is unable to paint the page till it’s finished.
So imagine how great it would be if the jQuery was already present on the visitor’s computer! This is why public CDNs are useful. If the visitor has already downloaded that particular file from the CDN on another computer, then they won’t have to download it again.
The Downside of CDNs – Domain Lookup
Whenever you add a resource from a new domain to your website, you introduce a delay for the DNS lookup. Ideally, these are supposed to be extremely fast, but in reality, it’s not always the case. Especially when we’re talking about visitors from areas where the Internet might not be as fast as we’d like it to be.
However, if a visitor as already resolved the name of a public CDN library in the past, it will cache that result and won’t have to resolve it again.
The Benefit and Downside of Cloudflare
Unfortunately, this also means that your visitor will always have to download jQuery, since they’ve never seen that URL before.
Use ONLY Popular Libraries
When choosing a public library, we want to maximize the chances that a visitor has:
- Already downloaded SOMETHING from it before (to avoid the extra DNS lookup)
Google’s Libraries are the ONLY One that Fit the Bill
To test this out, I used the Chrome Cache View tool to examine which files I’ve cached for the past six months. As you can see, the jQuery version used by WordPress was already downloaded onto my computer from Google:
This means that every subsequent request for this file from every other website would have a load time of “0”.
Note that most sites serve this jQuery from their own domain – including NameHero as shown here:
Now if we had loaded our jQuery from Google’s servers, this download would have been unnecessary. Here’s a tutorial on how to correctly serve your jQuery from Google’s servers instead of from your own.
I’m a NameHero team member, and an expert on WordPress and web hosting. I’ve been in this industry since 2008. I’ve also developed apps on Android and have written extensive tutorials on managing Linux servers. You can contact me on my website WP-Tweaks.com!