CDN Explained: How Content Delivery Networks Speed Up The Web
Why does a website hosted in Japan load instantly in New York? The answer is edge caching and Content Delivery Networks.
Defeating the Speed of Light
As we discussed in the latency article, the speed of light places a hard physical limit on how fast data can travel. If you are in New York and the web server is in Tokyo, every single image, video, and script file requested by your browser must travel across the Pacific Ocean, adding hundreds of milliseconds of delay.
To solve this, massive tech companies built Content Delivery Networks (CDNs). A CDN is a globally distributed network of proxy servers located in data centers all around the world.
Edge Caching
When the creator of a website utilizes a CDN like Cloudflare or Akamai, their website's static assets (images, CSS files, JavaScript) are copied and cached on every single server in the CDN's global network.
When you request that website from New York, the CDN intelligently routes your request to a server located just a few miles away in a Manhattan data center. Instead of traveling to Tokyo, your data only travels across the city. The website loads almost instantaneously.
Without CDN: User (NY) <--- Ocean (200ms) ---> Origin Server (Tokyo) With CDN: User (NY) <--- Local (10ms) ---> CDN Edge Node (NY)
Why This Affects Your Speed Test
Our global speed test utilizes CDN architecture. We host testing nodes in data centers across the planet. When you initiate a standard speed test, our algorithm automatically pings several nodes and connects you to the one geographically closest to your home.
This ensures we are testing the maximum capability of your local ISP connection, rather than the transit capacity of underwater trans-oceanic cables. If you want to see how geography impacts speed, try using our Global Ping Test tool to manually connect to distant nodes.