Issue with Borrowed Property Showing 'Not Set' Values in Purchase Event

Chris S. · 2025-09-25T13:27:49.046Z

I have added a borrowed property to my purchase event - the property is a filtering property from early in a user journey. I am seeing a high number of 'not set' values but when i look into individual users, i can see the property is set. Why are they not being copied over in the borrowed property?

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kapa.ai
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Hi Chris S., Please stand by as I search the Mixpanel knowledge base for an AI-powered answer. I normally take about 15 seconds or so. In case AI cannot answer your question, feel free to reach out to Mixpanel support at mixpanel.com/get-support. If you have follow-up questions for this thread, please tag me again with your question: @kapa.ai <follow-up question> 👋
Feel free to ask a follow-up question once I've answered by mentioning me with @kapa.ai
kapa.ai
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The most likely reason you are seeing a high number of "not set" values for your borrowed property, even though you can see the property is set for individual users, is due to the way Mixpanel's Borrowed Properties feature works:
- 7-Day Lookback Window: Borrowed properties only look back at events within a 7-day window prior to the target event (in your case, "purchase"). If the relevant event with the property you want to borrow occurred more than 7 days before the purchase event, the borrowed property will return "not set" for that purchase, even if the property exists for the user in their earlier journey.
- Most Recent Event Only: The property is borrowed from the most recent qualifying event within that 7-day window. If there are multiple events, only the latest one is considered. If none exist in that window, the value will be "not set" Borrowed Properties Reference.
So, if you are seeing "not set" values, it is likely because: - The event with the property you want to borrow is outside the 7-day lookback window from the purchase event. - The property was not set on the most recent qualifying event within that window.
To confirm, check the timestamps of the relevant events for users showing "not set"—if the source event is more than 7 days before the purchase, this is expected behavior.
For more details, see the official documentation: Borrowed Properties Reference.
kapa.ai is still learning and improving, please let me know how I did by reacting below.
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Chris S.
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kapa.ai why is the property sometimes missing from an event?
kapa.ai
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Let me check the knowledge base for you again. One moment! 📚
kapa.ai
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A property can be missing from an event in Mixpanel for several reasons:
- The property was not sent with the event: If the event was tracked without including the property, it will appear as “undefined” (or “not set”) in reports. For example, if you segment “App Open” by “Account type” and some “App Open” events did not include this property, those will be grouped as “undefined” Supported Properties Data Type.
- User profile property is missing: When segmenting by a user profile property, you’ll see “undefined” if the user profile does not contain that property, or if the event was triggered by a user without a user profile at all.
- Geolocation or default properties: For properties like City, Region, or Country, if Mixpanel cannot map the user’s IP to a location, or if the IP was not included in the request, these properties will be “undefined.”
- Event property only set on certain events: Sometimes, properties are only tracked on specific events in the user journey. If you try to borrow or segment by a property that isn’t always present, it will be missing from events where it wasn’t set.
- Data ingestion or tracking logic issues: There may be inconsistencies or bugs in the tracking implementation that cause properties to be omitted under certain conditions Product analytics implementation hiccups.
For more details, see the documentation on Falsy Values.
kapa.ai is still learning and improving, please let me know how I did by reacting below.
ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.

Issue with Borrowed Property Showing 'Not Set' Values in Purchase Event | Mixpanel Community

kapa.ai
APP
·
·
Hi Chris S., Please stand by as I search the Mixpanel knowledge base for an AI-powered answer. I normally take about 15 seconds or so. In case AI cannot answer your question, feel free to reach out to Mixpanel support at mixpanel.com/get-support. If you have follow-up questions for this thread, please tag me again with your question: @kapa.ai <follow-up question> 👋
Feel free to ask a follow-up question once I've answered by mentioning me with @kapa.ai
kapa.ai
APP
·
·
The most likely reason you are seeing a high number of "not set" values for your borrowed property, even though you can see the property is set for individual users, is due to the way Mixpanel's Borrowed Properties feature works:
- 7-Day Lookback Window: Borrowed properties only look back at events within a 7-day window prior to the target event (in your case, "purchase"). If the relevant event with the property you want to borrow occurred more than 7 days before the purchase event, the borrowed property will return "not set" for that purchase, even if the property exists for the user in their earlier journey.
- Most Recent Event Only: The property is borrowed from the most recent qualifying event within that 7-day window. If there are multiple events, only the latest one is considered. If none exist in that window, the value will be "not set" Borrowed Properties Reference.
So, if you are seeing "not set" values, it is likely because: - The event with the property you want to borrow is outside the 7-day lookback window from the purchase event. - The property was not set on the most recent qualifying event within that window.
To confirm, check the timestamps of the relevant events for users showing "not set"—if the source event is more than 7 days before the purchase, this is expected behavior.
For more details, see the official documentation: Borrowed Properties Reference.
kapa.ai is still learning and improving, please let me know how I did by reacting below.
ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.
Chris S.
·
·
kapa.ai why is the property sometimes missing from an event?
kapa.ai
APP
·
·
Let me check the knowledge base for you again. One moment! 📚
kapa.ai
APP
·
·
A property can be missing from an event in Mixpanel for several reasons:
- The property was not sent with the event: If the event was tracked without including the property, it will appear as “undefined” (or “not set”) in reports. For example, if you segment “App Open” by “Account type” and some “App Open” events did not include this property, those will be grouped as “undefined” Supported Properties Data Type.
- User profile property is missing: When segmenting by a user profile property, you’ll see “undefined” if the user profile does not contain that property, or if the event was triggered by a user without a user profile at all.
- Geolocation or default properties: For properties like City, Region, or Country, if Mixpanel cannot map the user’s IP to a location, or if the IP was not included in the request, these properties will be “undefined.”
- Event property only set on certain events: Sometimes, properties are only tracked on specific events in the user journey. If you try to borrow or segment by a property that isn’t always present, it will be missing from events where it wasn’t set.
- Data ingestion or tracking logic issues: There may be inconsistencies or bugs in the tracking implementation that cause properties to be omitted under certain conditions Product analytics implementation hiccups.
For more details, see the documentation on Falsy Values.
kapa.ai is still learning and improving, please let me know how I did by reacting below.
ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.