A Content Delivery Network places cached copies of your static content on servers distributed around the world, reducing latency by serving files from a location geographically close to each visitor. For websites with a global audience, a CDN can dramatically reduce page load times and decrease the load on your origin server.
How CDNs Work and When to Use Them
When a visitor requests a resource through a CDN, DNS directs the request to the nearest edge server. If the edge server has a cached copy, it serves it immediately. If not, it fetches the content from your origin server, caches it, and serves it to the visitor. Subsequent requests for the same resource from nearby visitors are served entirely from the edge cache.
CDNs are most effective for static assets: images, CSS stylesheets, JavaScript files, downloadable content, and video streams. Some CDNs also support dynamic content acceleration using techniques like TCP optimization, route optimization, and connection persistence to speed up even non-cacheable requests to your origin server.
Popular CDN providers include CloudFlare (which offers a free tier with basic CDN and DDoS protection), Amazon CloudFront (tightly integrated with AWS), MaxCDN (now StackPath, focused on performance), and Akamai (the largest CDN with the most extensive edge network). Choose a provider based on your traffic geographic distribution, integration requirements, budget, and the additional features like WAF and DDoS protection that many CDNs now bundle with their delivery service.