CDN (Content Delivery Network)
Short definition
A CDN copies a website's static files across servers around the world and serves each visitor from the copy nearest to them.
When a site is served from a single server, visitors far from it see slower load times. A CDN copies static assets, images, video, scripts, to servers in many countries and delivers whichever copy is geographically closest to the visitor.
This speeds up loading and takes load off the origin server, so the site stays up during sudden traffic spikes. Most CDNs also add a basic layer of security and attack filtering.
A CDN does not change the site itself, only how it is distributed; when content is updated, the cache needs refreshing too, otherwise an older version can keep showing for a while.
The basic attack filtering a CDN provides is often mistaken for a complete security solution, but that protection is only a surface layer. Separate measures such as server hardening and HTTP security headers are still needed against a targeted attack, a CDN does not replace them, it simply sits alongside them while it also speeds up delivery.
Why it matters
A slow-loading page loses visitors and drops in search rankings. For any business with an international audience, a CDN is the practical fix that makes the speed difference disappear.
Illustrative example
An event equipment rental business switched on a CDN for its overseas traffic, its image-heavy catalogue pages noticeably sped up within days.
