One common piece of advice you'll hear when you're trying to speed up your site is to “use a CDN”. A CDN stands for a content-delivery-network. 

A content delivery network is similar to a web server but there are two key differences:

1. CDNs store static assets. Like images, CSS files, and Javascript files. They don’t process web pages
2. Most medium-size websites have a single web server. But they can have dozens or hundreds of CDN locations around the world. And CDNs use geolocation to send visitors to the closest CDN.

Locations Around the World

Images alone are often 60% of a website's page load. When you include other static assets like CSS, & Javascript files it can go even higher.

If you have a CDN with locations around the world it’s like you always have a web server close to your customers – at least for those static files. That will drastically help the page load for those people.

In the image above you might be able to save 20 milliseconds without doing anything else to your site. Just being able to serve static files from a nearby server is timesaving.

CDNs Are Specialists

A CDN is a specialist. They specialize in storing & retrieving files. And your webserver is a specialist in processing & assembling web pages.

By using two specialists you’ll see speed gains over using a generalist for two jobs. I like to think of it like having a writer & editor work on a book compared to a writer which edits their own content. There’s nothing wrong with that but it might take longer.

CDN Options for WordPress

There’s a number of options for CDNs. Some managed WordPress hosts have a CDN built in. 

• WP Engine
• Kinsta
• Nexcess

And I'm sure there are plenty more. If your website host has a CDN I strongly recommend you use it – primarily because you’ll have easy access to support and if something goes wrong the host can fix the problem.

These CDNs often have dozens of locations around the world and your managed host bundles the cost into your hosting bill.

CDN Plugins

If your host doesn’t offer a CDN there are tons of CDN services out there. And they usually use a free WordPress plugin like CDN Enabler. 

And some of these CDNs also provide other services. Cloudflare is a really popular option that can also protect you from DDoS attacks, comment spam, and they have an upsell to be a CDN for video content in addition to images, CSS, & Javascript.

Budget CDN

If you’re on a budget and you host doesn’t have a CDN then I strongly recommend the CDN feature built into Jetpack. It’s really easy to turn on. All you have to do is connect your site to WordPress.com with a free account.

Testing a CDN for Speed Improvements

So how fast is all of this? Let's give it a go. I took two speed tests one without my hosting CDN enabled and one with.

For one of my sites it saves approximately .30 seconds. And that's a site with few images. If you have lots of static files you could see a bigger improvement.

There's a CDN option (CDN included with hosting, CDN service + plugin, free CDN in Jetpack) for each website & budget. The important point isn't to stress about the right CDN option – but instead of just sign up for one of them. Immediately. Because it will help people all over the world access your site.