A Content Delivery Network is a group of servers spread across many locations around the world that work together to deliver web content faster by serving it from the server closest to each user. Instead of every visitor hitting your origin server in one location, a CDN caches copies of your images, videos, CSS, JavaScript, and other static files at edge servers in dozens or hundreds of cities. When someone in Tokyo requests your website, they get served from a nearby CDN node in Tokyo rather than waiting for data to travel from your server in New York.
The speedup comes from reducing physical distance. Data travels through fiber optic cables at roughly two-thirds the speed of light, but over thousands of miles those milliseconds add up. A request from London to a server in San Francisco takes about 70 milliseconds for the round trip, and that is just the network delay before the server even starts processing. A CDN node in London cuts that to under 5 milliseconds. Multiply this across the dozens of requests a typical webpage makes, and the difference in page load time is very noticeable.
CDNs also help with reliability and traffic spikes. If your origin server goes down, the CDN can continue serving cached content. During a traffic surge, like a product launch or a viral post, the CDN absorbs most of the load so your origin server does not collapse. Many CDNs include DDoS protection, automatically detecting and filtering attack traffic before it reaches your infrastructure. They also handle SSL termination at the edge, keeping connections encrypted without adding load to your servers.
Popular CDN providers include Cloudflare, Akamai, AWS CloudFront, and Fastly. Modern CDNs go beyond static caching. They can run serverless code at the edge, optimize images on the fly, and handle video streaming. Setting up a CDN usually takes minutes: point your DNS at the CDN, configure caching rules, and the network handles the rest. For any website with users in more than one geographic region, a CDN is one of the simplest and most effective performance improvements available.