A content delivery network (CDN) is a group of servers spread across many locations that store copies of a website's content close to users, so pages and files load faster and the origin server carries less load.
A CDN caches copies of a site's static content, such as images, scripts, and stylesheets, on edge servers in many regions. When a user requests the content, it is served from a nearby edge server instead of the distant origin, which cuts the distance the data must travel.
Serving content from nearby edge servers reduces delay and speeds up load times, while offloading traffic from the origin server improves reliability and helps absorb sudden spikes. Many CDNs also add security features such as filtering malicious traffic.
CDNs are best at caching static assets that do not change per user, such as images, fonts, video, scripts, and stylesheets. Dynamic, user-specific responses are usually generated at the origin, though some CDNs can cache parts of them too.
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