Definition
A CDN (content delivery network) is a globally distributed network of servers, called points of presence or PoPs, that caches copies of your website and serves each visitor from the location physically closest to them. Instead of every request travelling back to a single origin server, often hundreds or thousands of miles away, the CDN answers from a nearby edge node in single-digit to low double-digit milliseconds, which makes pages load faster, takes load off the origin, lowers bandwidth costs, and adds reliability and security including DDoS filtering. This works best for static assets: images, CSS, JavaScript, fonts, video, and cacheable HTML; personalised or highly dynamic pages need more careful cache rules or bypass the CDN entirely. Almost every high-traffic or multi-region website uses one. Free CDNs (Cloudflare) and pay-as-you-go options (Bunny) cover most needs; enterprise CDNs (Fastly, Akamai, AWS CloudFront) handle the largest workloads and offer finer-grained control.
How it works
Your website lives on an origin server. A CDN keeps cached copies of your static content (images, CSS, JavaScript, fonts, and often whole pages) on hundreds of servers worldwide, called points of presence or PoPs. When someone visits, the request is routed to the nearest PoP. If the content is cached there it is served instantly; if not, the edge fetches it once from the origin, caches it, and serves every subsequent local request directly.
Why it matters
A CDN cuts page load times for global visitors, absorbs traffic spikes that would otherwise hit your server, reduces origin bandwidth costs, improves uptime when the origin briefly fails, and adds a security layer that filters attack traffic before it reaches you. For any site with audience in more than one region, it is the single highest-impact performance and reliability upgrade available.