Wirebook › Glossary › CDN (content delivery network)
What is a CDN (content delivery network)?
In one sentence: Copies of popular films, games and web pages kept in buildings close to you, often inside your internet provider's network, so they don't have to travel from far away.
A little more
A CDN keeps copies of popular things, films, game updates, pictures and web pages, on servers spread around the world, many of them inside internet providers' own buildings. When you press play, the film comes from the copy nearest to you instead of a single far-away server.
That makes things start faster (a shorter trip means lower latency) and stops the long-distance links from filling up, because one copy travels the long way and thousands of people then watch it locally. A CDN can't widen the last part of the trip, though: the pipe to your street and your house is the same whichever copy the film comes from.
See it in action
- BonusWhy does the internet slow down in the evening?Picture the internet as water: your house's pipe, one shared pipe under the street and a big main from far away.9 min · interactive
- BonusWhy does a video go blurry, then sharp?You press play and the picture is smudgy for a second, then it snaps sharp.8 min · interactive
- BonusWhy does the website still show the old picture?Compare the logo on a pretend server with the copy on your browser shelf.6 min · interactive
Do it for real
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