There are several reasons you might see “undefined” in your Properties list throughout Mixpanel reports when segmenting:
The specific Property you’re segmenting by isn’t always sent along with the Event you’re analyzing. For example, let’s say you’re segmenting the Event “App Open” by the Property “Account type” If there are instances where App Open fires without the Account type Property getting sent with it, these will be categorized as “undefined” when you segment by Account type. Another common example is UTM parameters - “undefined” represents users who fired an Event without any UTM in the URL that brought the user to your site.
When segmenting an Event by a User Profile Property, you’ll see “undefined” if there are User Profile Profiles that don’t contain that Property or if the Event was triggered by a user without a User Profile at all. For example, let’s say you’re segmenting the Event “Song Play” by the User Profile Property “Favorite Genre.” If there are Profiles that have triggered Song Play but don’t have the Favorite Genre Property, that value will be “undefined.” Triggers of Song Play by users without a User Profile will also show up under “undefined.”
Remove “undefined” & "null" values from reports
If you don’t want to see “undefined” or "null" values in your report, you can remove it by:
- Unchecking the “undefined/null” box in the visualization legend
- Looking only at instances where the Property in question “is set
This will exclude values where you see "undefiend" or "null"
- Directly exclude undefined or null values from an Insights visualization by hitting the exclude action.
If you’re getting “undefined” Property values but think you should not be, troubleshoot the issue using the Events page. Click on Filter in the top left to look at Events coming in where the Property in question “is not set.” You can then use this data to look at your code and figure out why some Events are being fired without that Property.