Short answer: Meta counts every install it touched within its own attribution setting, including view-through installs, and may model iOS results. Your MMP gives each install to one source. Some gap is normal; align windows, time zone and date basis before calling it a fault.
Why Meta's number is usually higher
Self-attributing network (SAN): an ad network, such as Meta, that decides itself which installs it drove and reports those claims, rather than the MMP matching a tracked click.
Meta's own developer docs say Facebook "generally has a larger attribution window" than most measurement partners. Add view-through claims and cross-network overlap, and Meta's figure will run above your MMP's.
How big a gap is normal?
There is no published standard. Meta's help centre only says MMP results "may be slightly different", typically because of windows. Track the gap over time and investigate when it moves, not just when it exists.
Likely causes
- Wider windows on Meta. Meta's help pages describe 1-day, 7-day and 28-day click settings for install reporting. If your MMP's Meta window is shorter, Meta keeps installs the MMP does not.
- View-through installs. Meta credits some installs after an impression with no click. Your MMP may not count these, or may give them to a later click elsewhere.
- Cross-network deduplication. If another network had the later click, the MMP gives it the install while Meta still counts it. See installs claimed by two networks.
- AEM modelling on iOS. Meta says statistical modelling may be used where reporting is incomplete, and modelled results are annotated in Ads Manager.
- Different date basis or time zone. New Meta ad accounts default to Pacific time, and Meta can report by impression time.
How to confirm it
- Note the attribution setting on each ad set you are comparing.
- Compare it with the Meta lookback windows in your MMP.
- In your MMP, filter Meta to click-through installs only and see how much of the gap remains.
- Switch Meta reporting to time of conversion and match the time zone, then compare weekly totals.
- Look up a sample of Meta-claimed installs in your MMP and see which source won them.
MMPs such as Linkrunner, Tenjin or Kochava let you set a lookback window per network, which is the setting to compare in step 2.
How to fix it
- Align click and view windows between Meta and your MMP where you can.
- Report both tools on the same time zone and conversion time.
- Use the MMP for cross-channel totals and budget splits.
- Use Meta's own numbers for optimisation inside Meta, where its model applies.
- Never add Meta's installs to other networks' installs to get a total.
| Gap shrinks when you... | Then the cause was |
|---|---|
| Filter to click-only | View-through claims |
| Match windows | Window length |
| Compare weekly | Date basis or time zone |
| Exclude iOS | AEM modelling or SKAN |
The Meta vs MMP troubleshooter walks through these checks in order, and the self-attributing networks guide explains why claims overlap.