CDN

Without a CDN, every visitor fetches every file from your one server, which may be thousands of kilometres away. A CDN caches copies in many cities and answers from the closest one, which cuts load times and takes most of the traffic off your server. It also absorbs traffic spikes and many attacks, and usually handles HTTPS for you.

What gets cached, and for how long, is controlled by HTTP headers such as Cache-Control, and a purge clears old copies after a change. Cloudflare, Fastly, Akamai, Amazon CloudFront and Bunny are standalone CDNs; Vercel, Netlify and Cloudflare Pages include one automatically.