Broadly speaking, and disregarding user-configured overrides, GA’s processing follows this sequence of checks:
AdWords parameters > Campaign overrides > UTM campaign parameters > Referred by a search engine > Referred by another website > Previous campaign within timeout period > Direct
Note the penultimate processing step (previous campaign within timeout), which has a significant impact on the direct channel. Consider a user who discovers your site via organic search, then returns via direct a week later. Both sessions would be attributed to organic search. In fact, campaign data persists for up to six months by default. The key point here is that Google Analytics is already trying to minimize the impact of direct traffic for you.
Contrary to popular belief, there are actually many reasons why a session might be missing campaign and traffic source data. Here we will run through some of the most common.
The classic direct-traffic scenario, this one is largely unavoidable. If a user types a URL into their browser’s address bar or clicks on a browser bookmark, that session will appear as direct traffic.
Simple as that.
When a user follows a link on a secure (HTTPS) page …read more