A Content Delivery Network (CDN) is a geographically distributed network of servers that cache and serve content to end users from locations physically near them. Instead of all visitors fetching data from a single origin server, a CDN stores copies on multiple servers across different regions and routes requests to the nearest available server.
How it works: When you visit a website using a CDN, your request gets directed to the edge server closest to your location rather than the origin server. This server delivers cached content (images, videos, stylesheets, HTML pages) directly to you. If the edge server doesn't have the content, it retrieves it from the origin server and caches it for future requests.
Key benefits:
- Faster page load times due to reduced distance data travels
- Lower bandwidth costs for your origin server
- Protection against traffic spikes, since load is distributed across servers
- Better performance for international audiences
- Some CDNs include security features like DDoS protection and Web Application Firewalls
Common gotchas: CDNs work best for static content like images and videos. Dynamic pages (user-specific content) may not benefit as much. Cache invalidation can be tricky - if you update content, old versions might persist on edge servers for a time. Most CDNs charge based on data transferred, so high-traffic websites need to factor this into budgets.
What to consider: Choose a CDN with edge locations in regions where your audience is concentrated. Check whether it supports the file types you serve most. Verify integration ease with your hosting provider or website platform.