Daryll Doyle WordPress Development and Consultancy in Cornwall

Parallelize WordPress Downloads


With more websites relying on bigger and better images in their design, website load times seem to be taking a big hit. Whilst this can be counteracted by offloading your images to a CDN (Content Delivery Network) that’s not always an option, especially when you’re on a budget.

At We Are DWM we recently worked on a WordPress website that was loading up to 50 images per page, this was leading to a huge delay in load times due to the fact that a web browser will only request around 6 resources concurrently from a single domain. As mentioned a CDN could help fix this and will probably be utilised in the future but we needed a quicker fix for this.

We opted to look at Parallelized Downloads, also known as domain sharding. Domain sharding is where you split website assets (styles, javascript, images etc) across multiple domains/subdomains. This allows your website to bypass the limit imposed by the browser and in effect allows the browser to download more assets at a time, increasing the speed of your page load.

As an example, the image below shows a waterfall of standard page load with a lot of images (we’ve limited the browser to three assets for the sake of the example). You can see that the browser is loading three images at a time and won’t download the others whilst it’s waiting.

Now in the next example you can see what happens when we use domain sharding to split the asset loading across two domains. As you can clearly see the load time for the images have been halved.

Whilst halving your page load time by using domain sharding is a little optimistic it can definitely help on sites where you need to load a lot of images.

At We Are DWM we decided to make setting up domain sharding as easy as possible for you and have released a WordPress plugin that makes setting it up a breeze. Simply set up your subdomains/domains and then enter them into the plugin’s admin area, the plugin will handle the rest for you.

Download the Parallelize Downloads plugin here or alternatively search for “Parallelize Downloads” within your WordPress admin plugin area.

Do keep in mind that domain sharding is only beneficial when you have an asset/image heavy website and if used wrongly can actually increase page load times due to increased numbers of DNS lookups.

Daryll Doyle WordPress Development and Consultancy in Cornwall