Guide
What is a CDN, and does a UK website need one?
A CDN (content delivery network) keeps copies of your images, scripts and pages on servers around the world, so each visitor downloads them from somewhere close. It helps most when your audience is spread across countries. If nearly all your visitors are in the UK and your hosting is in London, as ours is, a CDN is often optional rather than essential.
The idea
How a CDN delivers a page
- Visitor asksBrowser requests an image or page
- Nearest edgeThe CDN checks its closest server
- Cached copyIf it holds one, it replies at once
- OtherwiseIt fetches from your host, then keeps a copy
- Next visitorGets the stored copy quickly
Your own server is called the origin. The CDN servers close to visitors are called edge servers.
The problem it solves
Distance is a real cost
Data travels fast, but not instantly. Every request to a distant server adds delay, called latency, and a web page needs dozens of requests for images, stylesheets and scripts. A visitor in Sydney loading a site hosted in London waits noticeably longer than a visitor in Manchester, simply because of the distance and the number of network hops between them.
A CDN shortens that path. Rather than every visitor fetching files from one origin server, the CDN stores copies in many locations, called points of presence. The visitor is routed to a nearby one, so files arrive sooner and your origin server does less work.
That second benefit matters too. Because the CDN answers most requests for static files itself, your hosting handles fewer requests, which helps during busy periods and can soften small traffic surges.
What it does
What a CDN typically provides
Faster downloads
Images, CSS and scripts load from a nearby location, which helps visitors far from your server most.
Less load on your host
Static files are served from the edge, so the origin handles fewer requests.
Extra protection
Many CDNs absorb floods of traffic and offer a firewall in front of your site.
HTTPS handling
Certificates and modern protocols are managed at the edge.
Image tools
Some CDNs resize and convert images on the fly to suit each device.
Resilience
Cached pages can still be served for a short time if the origin has a problem.
Fast already, from London
LiteSpeed servers in London with caching built in, on every plan.
Decision
Do you need a CDN?
A CDN is worth it when
- You sell or serve visitors in several countries
- Your pages are heavy with large images or video
- You expect big traffic spikes
- You want an extra firewall layer
- Your audience is far from your server
You can probably skip it when
- Nearly all visitors are in the UK
- Your host is in London already
- Your site is small and well cached
- You prefer fewer moving parts
- You have not yet fixed images and caching
UK sites
The UK-only business case
Within the UK the distances are short. A visitor in Glasgow reaching a server in London experiences a delay of a few milliseconds, which is tiny compared with the time spent building the page, downloading oversized images or waiting for slow scripts. For these sites the biggest gains almost always come from page caching, image optimisation and a lean theme, not from a CDN.
That is why we suggest fixing those first. Our hosting uses the LiteSpeed web server with built-in caching, and Redis object caching is available for dynamic sites, all on UK servers in London. For a local business whose customers are in the UK, this combination delivers fast pages without adding another service to manage.
A CDN becomes more attractive if you sell abroad, have a large international audience, serve video, or run a shop with many product photographs viewed from different countries. Even then, add it after the basics are in place.
Comparison
Caching on your host and a CDN compared
| Factor | Server caching | CDN |
|---|---|---|
| Where copies live | On your web server | On many servers worldwide |
| Main benefit | Pages built once and reused | Files delivered close to the visitor |
| Helps distant visitors | Limited | Strongly |
| Helps UK visitors | Strongly | Modestly |
| Extra cost | Usually included | Often free tier, paid for more |
| Setup | Plugin or setting | DNS or plugin change |
| Can cause problems | Stale pages if not cleared | Stale files, mixed content, extra complexity |
Trade-offs
Costs and downsides to weigh
Many CDNs offer a free tier, which is appealing, but check the terms. Paid plans are priced by the amount of data transferred, features or both. There may also be limits on image processing or firewall rules, and support levels differ.
Complexity is the larger cost. A CDN is another service in the chain. If a page shows an old image, you must know whether the browser, your server cache or the CDN is serving it. Certificates, redirects and cookies need to be configured to work together, and a mistake can cause a redirect loop or a security warning.
There is also a privacy angle. A CDN processes your visitors' requests, so it is a data processor in the sense used by UK data protection law. Mention it in your privacy notice, and read the provider's data terms. For guidance, see the Information Commissioner's Office website. This is general information, not legal advice.
If you add one
Setting up a CDN sensibly
Fix the basics first
Compress images, enable page caching and remove unneeded plugins. A CDN cannot rescue a bloated page.
Measure before
Record load times from a few locations, and see how to test website speed.
Choose a CDN and connect it
Either change DNS records so traffic passes through it, or use a plugin to rewrite file addresses. DNS explained helps here.
Set cache rules
Cache images, CSS and scripts for a long time. Do not cache baskets, checkouts or logged-in pages.
Test everything
Check forms, login, checkout, HTTPS and mobile.
Measure after
Compare against your baseline, and keep the CDN only if it helps.
Pitfalls
Common CDN mistakes
- Caching pages that should be personal
- Forgetting to clear the cache after changes
- Leaving mixed HTTP and HTTPS links
- Running two overlapping optimisation plugins
- Ignoring the origin server's speed
- Setting very short cache times
- Not testing from outside the UK
- Assuming a CDN fixes huge images
Worked example
Two example businesses
Consider a Manchester dental practice. Its visitors are local, the site is a few pages with modest photographs, and it is hosted in London. A CDN would shave a few milliseconds off each file, which no patient would notice. The time is better spent making sure the images are small and caching is on.
Now consider a UK maker who ships handmade goods to the United States, Australia and Europe, with a shop full of large product photographs. Visitors far from London wait longer for every image, and a CDN can noticeably improve their experience and reduce load on the host. Here the extra service is easy to justify.
Most small businesses look like the first example. If you are unsure, test your site from a distant location and from the UK using the steps in our speed testing guide. If the difference is large and your customers really are overseas, consider a CDN. If not, spend the effort elsewhere.
FAQ
Common questions
Is a CDN the same as web hosting?
No. Hosting is where your site lives. A CDN is an extra network of servers that stores copies of its files closer to visitors.
Will a CDN improve my SEO?
Only indirectly, by making pages faster, which can help user experience and Core Web Vitals. Speed is one of many factors.
Do your plans include a CDN?
Our plans include LiteSpeed caching, Redis object caching and UK servers in London. You can add a separate CDN service if your audience is international.
Is a free CDN good enough?
For many small sites, yes. Check the data terms and limits first.
Can a CDN break my site?
A misconfigured one can cause old content, redirect loops or broken checkouts. Test carefully and keep the settings simple.
Keep reading
Related pages
Fast UK hosting, with caching included
LiteSpeed and Redis on servers in London.