A Content Delivery Network (CDN) caches copies of your website, images, videos and other assets on servers located in data centres around the world. When a user requests content, the CDN serves it from the geographically nearest server rather than your origin server, dramatically reducing latency and bandwidth costs.
CDNs work by intercepting requests through DNS routing or a CNAME record that points traffic to the CDN's infrastructure. The CDN's edge servers store cached copies of static and dynamic content. On first request, content is fetched from your origin and cached; subsequent requests hit the edge server. Cache expiration is controlled by HTTP headers and TTL values you configure.
How it improves performance:
- Reduces round-trip time by serving from nearby locations
- Offloads bandwidth from your origin server
- Absorbs traffic spikes across distributed infrastructure
- Often includes HTTPS termination and DDoS mitigation
Common use cases:
- Serving images and video to global audiences
- Accelerating static assets (CSS, JavaScript, fonts)
- Protecting origin servers from direct exposure
- Ensuring consistent performance across regions
TipCDNs are most effective for static or semi-static content. Personalized or real-time dynamic content may see less benefit and still requires origin requests.
Many CDN providers also act as a reverse proxy, sitting between users and your origin, and can include uptime monitoring and status pages to track availability across regions.