A website can be composed of a bunch of files that your browser downloads and then renders to what you see on your device.

One type of file is javascript code, which sometimes can be relatively large, like several megabytes (MB). If a website gets hit by a lot of users, those MBs add up, and can chew through the bandwidth allotted for the given website. Consuming more bandwidth can cost more money for the website operator, who pays a hosting company for the website’s resources (disk space, compute time, network bandwidth).

To help alleviate this, and to also make these downloads faster around the world, Content Distribution Networks(CDN) exist. The idea is that you upload your large files to the CDN, and then have your website link to those big files, and now your website has offloaded the big downloads elsewhere. However, contracting with a CDN costs money too, just maybe not as much as a website’s host charges.

This brings us back to the case in from this post. What the dev did, was choose not to pay for a CDN to link to, but used archive.org’s copy of the large file to link to. So when a user loads the website, all of the big bandwidth hog files are being served for free from archive.org. But it’s really not free from archive.org’s perspective, since they’re the ones ultimately paying for the bandwidth.