Using evars rather than props?

Question

Is there a purpose to mapping a variable to both eVar and prop? Or is it best practice to map to only eVar or only prop (not both)?

Vinay_Chauhan · Accepted Answer

Hi ​@alchanAccording to me, in most cases, mapping a value to both an eVar and a prop is unnecessary and not considered best practice anymore.Earlier, props were used for pathing and real-time reporting, while eVars were used for persistence and attribution. These days, eVars support persistence, attribution, segmentation, and participation, which covers the majority of use cases that props were originally meant for.Best practice is -Use eVars for anything you want to analyze over time, attribute to conversions, or segment users by.Use props only when you specifically need hit-level pathing or very short-lived values that should not persist beyond the hit.Mapping the same value to both should only be done for a clear, intentional reason (such as legacy reporting or specific pathing needs). Otherwise, it adds complexity without meaningful benefit.

Jennifer_Dungan · Answer

There is little use any longer to mapping the same value to a prop and an eVar any longer… there is an “instance” metric associated to each eVar, so you can still properly identify where the value was explicitly set (as well as where the value persisted).

In the past, eVars could only be correlated with eVars, and props could only be correlated with props (except for in Data Warehouse)… so it was more common back in the day to double track everything… and not having Workspaces and a lot of the current functionality, it was much harder to get the data you needed. With those advancements, most companies moved away from the double tracking. (Which was also hard when you had 75 props and 250 eVars… it could never be fully 1 to 1)

That said, props do have an added bonus of having a specific “Entry” or “Exit” value; which is the first or last value collected in the prop for the visit (it is not specifically the entry or exit to the site). Some businesses find this useful to identify this, and so in those cases, they will sometimes track the value in both, to leverage the persistence available in the eVar, but also the “pathing” features of props…

I haven’t tried, but I feel that with advanced segmentation, you should be able to get the first / last value of an eVar…

That said, if you see benefit and reasons to track it in both, that’s your choice, we can’t answer that for you.

I prefer to keep my implementation clean. I use props and eVars for Hit level tracking (eVars for longer values to avoid truncation), and then eVars for persisted values. Making full use of my available dimensions and limiting redundancy.

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