Recently a URL was posted on Ask Different that looked like this:
Why does it have the "?as=1" at the end of it? I understand that it is part of the workings of the website, but what is its purpose?
I've been exploring since yesterday in response to this comment and have found the following so far:
?cb - A link from the community bulletin of a site.
?newsletter - A link to a question from the emailed community newsletter. Also includes ?nlcode
?rq - A link to a question from the related questions sidebar.
?lq - A link to a question from the linked questions sidebar.
?atw - A link from a site's automated Twitter feed.
?stw - A link created by the share button posted automatically to Twitter.
?sgp - A link created by the share button posted automatically to Google Plus.
?sfb - A link created by the share button posted automatically to Facebook.
?sem - A link created by the know someone who could answer this question box sent via email
?blb - A link to a community blog/Stack Exchange blog from the footer on the main site.
?noredirect - Stops a migrated question from automatically redirecting to its new location. Additionally, for logged-out users, stop an unanswered duplicate from redirecting to its target.
?__ - Contains a random value; used to switch between the full site and the mobile site.
Some suffixes have since been removed in subsequent redesigns:
We slap slugs onto links in places where we're looking for hard numbers about usage. Click through rates, visitors per share, that sort of thing.
It's a decidedly low tech approach that has a couple of benefits.
+ "?blah=1"in the right places to turn this on and off
Offhand, I know we're looking at newsletter links, the site drop down, the hot question drop down, and shared links (Twitter, Facebook, Google+).
The data we collect can be used for figuring out whether certain features are worth keeping around or promoting. Sometimes it's just trying to measure the effectiveness of changes.
Actually, Kevin is correct. It's just to let Stack Exchange's staff know how are things going.
All sites in the dropdown menu have
?as=1 appended and all hot questions' links have got