Why
Sometimes a conversion tag only needs to be fired if a visitor was referred by a certain affiliate website or other source. For example: we run an affiliate program at Tradedoubler and we need to be sure that only the conversions made by visitors referred by Tradedoubler are attributed as a conversion in Google AdWords.
This data used to be available in Google Analytics’ UTMZ cookie. Since Google Universal Analytics was introduced, the UTMZ cookie is no longer available. We can solve this by creating a custom tag that saves the utm source in the browser’s local storage and a custom variable that makes the saved utm source accessible in our triggers.