What is a CDN?
A CDN, or content delivery network, is a group of servers spread across many locations that each hold a copy of your website's files. When someone visits, they are served from the nearest one instead of from wherever your hosting lives. Less distance means faster pages and less strain on your main server.
The warehouse version
Picture a business that ships everything from one warehouse in Cornwall. Orders from Truro arrive the next morning. Orders from Edinburgh or Amsterdam take longer, simply because of the distance. A CDN is the same business opening small depots in every major city, stocked with its most popular items. Wherever the order comes from, it goes out from somewhere nearby.
What a CDN actually does
- Serves files from nearby: images, styles, scripts and often whole pages are delivered from the closest location, called an edge server.
- Takes load off your hosting: most requests never reach your main server, so a busy day or a post going viral is far less likely to slow the site down.
- Soaks up attacks: large CDNs sit in front of your site and can absorb floods of fake traffic, known as DDoS attacks, before they reach it.
- Keeps copies ready: a CDN is a form of caching, just spread around the world instead of sitting in one place.
Common CDN providers
Does a small business need one?
It depends on who visits. If almost all of your customers are in the UK and your hosting is in the UK, the distance saving is small. The load and security benefits still apply, though, and many good hosts now include a CDN as standard, so there is often no extra cost or setup to think about.
Where a CDN earns its keep is a site with visitors spread across the country or abroad, a site heavy with images, or a business that gets sudden bursts of traffic from adverts, press or social media.
The one thing to know
Because a CDN serves saved copies, a change you have just made can take a little while to appear everywhere. Clearing, or "purging", the CDN cache fixes it straight away. It is the same trade-off as any other cache: a short delay on updates in exchange for much faster pages the rest of the time.
The takeaway
- A CDN serves your site from locations close to each visitor.
- It also reduces load on your hosting and helps absorb attacks.
- For UK-only audiences the speed gain is modest, but the other benefits still count.
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