What is CDN Caching?
CDN caching is the process of storing copies of your website's content on servers distributed across a global network of edge locations. When a visitor requests content, it is served from the nearest edge server rather than the origin server, dramatically reducing latency and load times.
How Does CDN Caching Work?
CDN caching works by intercepting requests for your website and checking if the requested resource exists in the edge server's cache. On a cache hit, the content is served directly from the edge location. On a cache miss, the CDN fetches the content from the origin server, serves it to the visitor, and stores a copy for future requests. Cache behavior is controlled through HTTP headers like Cache-Control, Expires, and ETag, along with CDN-specific configuration rules.
Effective CDN caching can offload 80-95% of traffic from your origin server, reducing hosting costs and improving reliability. Static assets like images, CSS, JavaScript, and fonts are ideal for CDN caching with long TTLs (time to live). Dynamic content can also be cached at the edge with shorter TTLs or using stale-while-revalidate strategies. Major CDN providers like Cloudflare, Fastly, and Amazon CloudFront offer sophisticated caching rules, cache purging APIs, and analytics to optimize cache hit ratios.