Compare Future sell-through reports and line item forecasts

In Google Ad Manager, there are two main ways to predict availability:

• Line item forecasts appear when you click Check inventory when creating or viewing a line item and provides a forecast focused on a single line item. This can help you maximize the number of impressions for that particular line item and targeting.
• Future sell-through reports are a report type that displays availability across your entire Ad Manager network. Future sell-through reports can help you determine whether you have space to book more line items.

Summary of differences

The table below summarizes differences between interactive forecasting and future sell-through reports. Note that there might be additional differences in behavior not covered here.

	Check inventory forecast	Future sell-through report	Possible discrepancies
Adjustments	Manual and historical adjustments taken into account.		N/A
Booked line item data freshness	Up-to-the minute	Daily	Future sell-through reports are more likely to overestimate available inventory due to activity since the report was started.
Creatives	The line item's "Creative count" can significantly affect forecast. To more accurately compare results, next to "Expected creatives": a. Add a creative size. b. Under "Count," enter a high number of creatives, such as 10. Note: To enter a count, you might have to click Show creative details. Counts aren't available for master/companion display ads. c. Under "Creative targeting," make your selections. Line item forecasts account for serving restrictions such as frequency capping and roadblocks. For example, if the creative details specify it can fill only one ad slot on a page (which is the default), this will reduce the available impressions.	No simulation occurs during the creation of a Future sell-through report. Only the counting of rows that match dimensions/filters takes place. This means there's no special logic for recognizing creative counts or special ad unit hierarchies.	Future sell-through reports might show more availability than interactive forecasting.
Maximum look ahead	Two years	90 days for daily-granularity data; 1 year for monthly granularity data.	N/A
Special ad units	Impressions from special ad units are generally excluded while computing forecasted impressions. This includes impressions from special ad units that are parts of placements or for which parent ad units are targeted. The exception is when special ad units are explicitly targeted in the line item.	No simulation occurs during the creation of a Future sell-through report. Only the counting of rows that match dimensions/filters takes place. This means there's no special logic for recognizing creative counts or special ad unit hierarchies.	In check inventory, special ad units must be explicitly targeted. In future sell-through, they might be implicitly targeted through parent ad units or placements.
Simulation	Simulation runs in real time with each request for the time period of the proposed line item.	Simulation for data  (used as the basis for FSTR) runs for an 18-month time period.	For competing line items with date ranges that extend outside the time window being forecasted, Ad Manager estimates the number of impressions that will compete.