What is the difference between Unique Actions / Actions?

I just realized I’m not really sure what the difference between Actions and Unique Actions is.

I use trackEvent with a bunch of Custom Dimensions to track User Input to one of my search forms. The report in some cases shows very different results for actions and unique actions.
Although all custom dimensions are only stored via this same event, the total numbers of the unique actions are different from the total numbers of the actions.

Am I correct in assuming that a readjustment of the search form counts edited fields as new unique actions (now two actions), but the unedited ones are only counted as action (the same as before - so instead of two actions one), but not as unique action?

I’ve always thought about it this way: Every action (pageview, event, etc) is part of a session. If a specific action is repeated (so an action with the exact same values for whatever dimensions it happens to set) in a session then it will still be only a single unique action in that session.

At least that’s what I’ve always assumed.

I’ve been wondering about this, as well. From what I’ve seen thus far using Unique Event Actions in custom reports, session seems to be irrelevant. I set up the following within a custom report:

  • Dimensions: Event Action
  • Metrics: Unique Event Actions
  • Filter: Event Category = Search

My goal is to track usage of search terms, search suggestions selected (from an AJAX dropdown), and submission (suggestions didn’t help).

I’m getting “1” for all actions, which leads me to believe that it’s comparing only the action name, regardless of whether it’s the same visitor / session.