Study first
Review the ideas behind the questions
Review what GA4 Data Import can and cannot add before a campaign dashboard relies on it. Focus on join timing, campaign tag matching, required upload fields, user-data prerequisites, custom event-data limits, and import health checks.
Know how the import joins
GA4 Data Import joins external data with Analytics data, but the join timing depends on the import type. That difference affects reports, audiences, exports, and cleanup plans.
- GA4 Data Import joins external uploaded data with Analytics event data.
- Collection or processing-time imported data is not joined with Analytics historical data that has already been processed.
- Reporting or query-time imports are temporary joins used when a report is opened and cannot be used when creating audiences or exploration segments.
In Practice
Join timing affects promises
Before promising an audience, segment, export, or report use case, check whether the import type joins at processing time or query time.
Deletion behaves differently by join type
If a query-time source is deleted, future query joins stop. Processing-time joins that already happened can remain and may need data deletion or user deletion.
Common mistakes
Assuming every import type can feed GA4 audiences and exploration segments.
Check the join type first because query-time imported data is not available for creating audiences or exploration segments.
Q&A
What does GA4 Data Import join?
It joins external uploaded data with Analytics event data.
Can query-time imported data create GA4 audiences?
No. Query-time imported data is not available when creating audiences or exploration segments.
Match campaign imports to campaign tags
Campaign data import depends on exact campaign tagging and required file fields. Small naming changes can fragment reports or lower match quality.
- GA4 campaign data import combines non-Google campaign data such as cost, clicks, and impressions with Analytics revenue and key-event data.
- Campaign source parameter (utm_source), medium parameter (utm_medium), campaign name (utm_campaign), and date values in the import file must exactly match logged session values.
- Campaign source parameter (utm_source), medium parameter (utm_medium), and date are required dimensions for campaign data import.
In Practice
Case changes can break matching
Treat campaign tag values as join keys. A source value written two ways can split or miss matches even when the campaign looks the same to a person.
Currency belongs in the quality checklist
If cost is imported, the file mapping must include a currency field or a hardcoded currency value. Otherwise the cost import is not ready.
Common mistakes
Uploading campaign cost data while destination URLs use inconsistent source and medium values.
Standardize campaign source parameter (utm_source) and medium parameter (utm_medium) values before relying on imported cost reporting.
Q&A
Which campaign import dimensions are required?
Campaign source parameter (utm_source), medium parameter (utm_medium), and date are required.
What happens if cost is included in the import?
A currency field or hardcoded currency value is required for the cost import.
Read import health before acting
After upload, the safest next step is to check import health and availability windows. Different import types expose different status details and reporting timing.
- Campaign data import health includes percent imported and match rate.
- Campaign data can take up to 24 hours after upload to become available in reports, audiences, and explorations.
- User-data import needs user-scoped custom dimensions created before upload when imported values should appear in reporting.
In Practice
Match rate is not the only visibility clue
A low match rate points to join issues, but a fresh upload may still need the documented availability window before reports are final enough to review.
Duplicate keys are a real import risk
Do not treat duplicate key warnings as cosmetic. They can cause reporting issues, including double counting for custom event data imports.
Common mistakes
Treating a blank user-data import match rate as proof the upload failed.
Use the user-data import rules for that import type because percent imported and match rate are always blank for User Data import.
Q&A
What does percent imported measure for campaign data import?
It is the number of rows successfully imported divided by the number of rows in the import file.
What should be created before importing user values for reports?
Create the matching user-scoped custom dimensions before the upload.