What is CDN?
A CDN (Content Delivery Network) is a network of geographically distributed servers that cache and serve a site's static assets from a location near each visitor. A CDN reduces latency and offloads traffic from the origin server.
Why CDN matters
Light travels only so fast: a visitor in Sydney requesting a page from a server in Frankfurt waits roughly 300 ms for a round trip before anything else happens, and a page needs several. A CDN keeps copies of your static files (images, CSS, JavaScript, fonts, often whole HTML pages) on servers around the world and answers from the nearest one, which cuts that latency to a few milliseconds and takes most of the load off your origin.
Modern CDNs do more than caching: TLS termination, compression, image resizing, HTTP/3, bot filtering and DDoS absorption. Setting one up has shrunk to a DNS change on services such as Cloudflare or Bunny, and the main configuration decision is what to cache and for how long, which is governed by the cache headers your origin sends.
Example
Verifying that the CDN is actually serving a file:
curl -sI https://example.com/logo.png | grep -iE 'cf-cache-status|x-cache|age'
cf-cache-status: HIT
age: 8231HIT means the edge answered; MISS or DYNAMIC means the request went to your origin.
Common mistakes
- •Putting the CDN in front and never checking whether anything is cached (a
no-storeheader from the origin defeats it). - •Caching HTML that contains personalised content such as a logged-in user's name.
- •Forgetting to purge or version files after a deploy, so visitors get stale CSS.
How Webmatik checks it
Webmatik does not require a CDN, but the Real visitor load time, Server response speed and Page file compression checks are where a missing or misconfigured one shows up, and the performance guides explain how to read them.
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