Why does Disqus not use global CDN for it's comment code?
cdn, disqus, javascript
Solution
Actually they are using a CDN to deliver `count.js`.
If `<shortname>` exists
`http://<shortname>.disqus.com/count.js` redirects to something like
`http://mediacdn.disqus.com/1334018047/build/system/count.js`.
To reduce traffic `count.js`(on the CDN) is delivered with an Expires-Header that allows caching it up to a month.
But imagine they need to change the code or block some sites or deliver special features to others, it would take up to a month until all clients get the changes. To reduce that timespan they probably use this redirect (which is cached for only up to 10 minutes), so code/feature changes will reach every client within 10 minutes.
It gives them a lot of flexibility and does not require the user to change the include code ever.
Problem
According to the Disqus comment code instructions, you're supposed to include their JavaScript as follows: ``` (function () { var s = document.createElement('script'); s.async = true; s.type = 'text/javascript'; s.src = 'http://' + disqus_shortname + '.disqus.com/count.js'; (document.getElementsByTagName('HEAD')[0] || document.getElementsByTagName('BODY')[0]).appendChild(s); }()); ``` The location of the JavaScript is based on a shortname that is specific to your site. Why does Disqus do that instead of using one global location for their JavaScript (e.g. cdn.disqus.com/count.js). If the JavaScript is the same for each site, it seems silly to require everyone to redownload the JavaScript for each Disqus-enabled domain they visit. If the JavaScript is different based on the shortname, why not just use a shortname variable that gets set before the global js is loaded? Disqus is a fairly large and sophisticated company, so I'm assuming that this is a conscious and purposeful decision on their part. Why did they go this route?