I captured a hit that i am sending to Universal Analytics.
/collect?v=1&_v=j31&a=1233968061&t=item&cu=SEK&_s=3&dl=siteaddress&de=UTF-8&dt=online shop&sd=24-bit&sr=1920x1200&vp=1903x1065&je=1&jid=&cid=97152128.1418127174&tid=UA-Test-1>m=GTM-Test&cm1=desktop&z=1167078446
(is just a part of it)
Does anyone know what the "a" parameter represents? I could not find anything in the Protocol Parameter Reference about it.
The 'a' parameter is a random number generated and used to link Google Analytics to Google Adsense. It is the equivalent of utmhid used in Google Analytics classic version.
[the reference doc for the classic version is here: https://developers.google.com/analytics/resources/concepts/gaConceptsTrackingOverview?hl=en]
My source is the Google Analytics team directly as my company, DMPG.co.uk is a certified partner.
I wrote the cheatography sheet at http://www.cheatography.com/dmpg-tom/cheat-sheets/google-universal-analytics-url-collect-parameters/ and have now updated it with this information.
ps. sorry for being nearly a year late to the party on this one!
According to Google's Measurement Protocol parameter reference, 'a' is not a valid parameter, so I think you can remove it and it will not affect your tracking.
It is perhaps a typo and should be 'ea' or 'pa' etc. But the reference above should be the source of truth you need.