29 October 2026·3 min read
The two-month retention trap — why only Explorations come up empty
Standard reports happily show last year, but the same period in an exploration is blank. GA4 keeps event-level data for two months by default, and once it is deleted no setting brings it back. A one-minute change that gets more expensive every month you leave it.
Symptom
Planning for the season, you open an exploration to look at the same period last year. You set the date range and the table is empty. Changing dimensions does not help; removing the segment does not help.
What makes no sense is the standard report. Open the same period there and sessions and users are both fine. Present in one place, absent in the other — so you assume the exploration is broken and spend an hour changing conditions.
Cause
GA4's event data retention defaults to two months. On the free tier you can choose between two months and fourteen; if nobody touches it, it stays at two. Event-level and user-level data older than that is deleted.
Only one side goes blank because the two screens read different things.
| Where you look | What it reads | Effect of retention |
|---|---|---|
| Standard reports | Tables aggregated once a day | None — the numbers stay |
| Explorations, the Data API | Event-level and user-level raw data | Gone once the retention window passes |
That is what makes this defect quiet. The dashboard you check every morning covers years; only the deep analysis you do a few times a year exposes it. And by then it is too late.
"Too late" is not an exaggeration, because this is the kind of defect that cannot be undone. Changing the setting to fourteen months does not bring back what was already deleted. Change it today and it accumulates from today; everything deleted up to yesterday is permanently gone. The cost of this item is not the minute it takes to set — it is the number of months it went unset.
AnalyticScan scores this at four points and fails it outright at two months. It carries the largest weight in the ST (property settings) category, not because it is the easiest to fix, but because it is the one item where what you postpone is never recovered.
How to check in GA4
1) Read the current setting. Admin → Data collection and modification → Data retention. If it reads two months, this applies to you. Thirty seconds.
2) Find out how far back you still have. In an exploration, move the date range to three months ago, then six, and see where values stop. That boundary is what you actually still hold.
3) Compare with the standard report. If the same period exists in the standard report and not in the exploration, that confirms it. If both are empty, this is not retention — collection itself stopped during that period, which is a different problem.
How to fix it
Change it to fourteen months and save. That is the maximum on the free tier and it costs nothing. It is a property setting, so it needs Editor access or above, and the change can take about a day to take effect. Nothing already deleted returns, which is exactly why it is worth doing while you are reading this rather than later.
Look at the user-data reset option on the same screen. It restarts a user's retention period whenever that user is active again. For services people come back to often, leaving it on helps user-level analysis.
If fourteen months is still short, that is the BigQuery export. Fourteen months covers year-on-year comparison, but comparing against two years ago, or keeping raw events for the long term, is not something GA4 solves internally. Exported data lives in your own project regardless of GA4's retention window. It too starts from the day you enable it — switching it on today does not produce last year.
Note the date you changed it. For whoever investigates "why is there nothing before this point" in a few months, one line of notes is the cheapest possible answer.
In one line
A healthy standard report does not mean the data is there. At two months, the raw data explorations need is being deleted every month, and deleted does not come back. It is a one-minute change in the admin screen, so making it today beats making it tomorrow by exactly one day of data.