# Why does the elementary OS download URL seem to contain a unique tracking code?

http://sgp1.dl.elementary.io/download/QTT3MWI6NFUy3N==/elementaryos-0.3.2-stable-amd64.20151209.iso


(Note: I have changed the actual code)

• what is actual code? – Ravan Dec 28 '15 at 6:44
• 405 not allowed – JulianLai Dec 28 '15 at 8:21

It's a time-code that stops hotlinking. It's not tracked, although your button click is.

Hi there! I built both the system to generate those links and manage the delivery network that delivers the downloads, so I'm quite qualified to answer this, although Ravan has it mostly covered.

The elementary.io website is actually open-source in itself, and the code that generates (most) of this link can be seen in /_backend/classify.current.php, Line 14. That line is this:

$download_link = '//'.$region.'.dl.elementary.io/download/'.base64_encode(time()).'/';

You see the bit about time in the variable? It's basically encoding the time, and the download server decodes it, and checks it's within the last few days. If not, it tells you to get a new link. This is to combat hotlinking leeching bandwidth off of our servers, something several sites had been doing previously. This is why you get 405: Not Allowed, the link expired.

As for your visits and actions on the site, you should review the Privacy Policy, and maybe /_scripts/pages/download.js, Line 174 for what gets sent when you click download. To summarise, it's just the Architecture, Method, Region, and your previous OS (Windows, OS X, or Linux).

• +1 for info, what is QTT3MWI6NFUy3N ? how to decode it? – Ravan Dec 28 '15 at 11:16
• QTT3MWI6NFUy3N== doesn't decode because the original asker changed it, thinking it might be something to keep private I assume. MTQ1MTI4ODc1MA== (one of yours) is 1451288750, which in unix time is 2015-12-28T07:45:50+00:00. You can do your own conversions on base64decode.org and unixtimestamp.com – Lewis Goddard Dec 28 '15 at 11:20
• there I missed to convert from timestamp. :D I suggest, include those two links in asnwer :) – Ravan Dec 28 '15 at 11:25
• Why is hotlinking a problem in the first place? Don't you want people to be able to link to an iso directly, for example in customized installation tutorials? – phihag Dec 28 '15 at 19:48
• We've used around a petabyte of transfer on our delivery network. Unfortunately, we don't have our own multi-millionaire funding things, so this causes problems if lots of people link there. Our site balances downloads between regions, dumb direct links do not. If people want to direct link, we are happy for them re-host it themselves, and I even point out to people when I see outdated copies. They could also link to the magnet links instead. – Lewis Goddard Dec 29 '15 at 9:28