About overlapping audiences

Having overlapping audiences is not necessarily a bad thing, but it can lead to poor delivery of your ad sets. This is because when ad sets from the same advertiser are going to end up in the same auction (meaning they're targeting similar audiences), we enter the one with the best performance history and prevent the others from competing to get shown. We do this so that your ads are not competing against each other, which can drive up costs and lead to inefficient uses of your budget. You can check whether two audiences you're using are overlapping with our tool:

1. Go to your Audiences.
2. Tick the boxes next to the audiences that you want to compare (up to five).
3. Click Actions > Show audience overlap.

Notes:

• The first audience that you select will be listed first as the "Selected audience". Every other audience that you select will be listed in the Comparison audiences section. You can change the selected audience by choosing a new one from the drop-down menu in the top right-hand corner of the tool. You can choose from any of the audiences that you selected.
• You can only get useful overlap information from audiences with at least 10,000 Accounts Centre accounts, so consider that when selecting which audiences to compare.

The tool will show both the "Overlap" and the "% overlap of selected audience". The Overlap column shows the number of Accounts Centre accounts that are in both audiences. The "% overlap of selected audience" column compares the number of Accounts Centre accounts that are in both audiences to the total number of Accounts Centre accounts in the selected audience to show the percentage of overlap. This column is why the selected audience is separate from the comparison audience. Here's an example to help explain:

Say you have a selected audience with 1,000,000 Accounts Centre accounts (we'll call this audience A) and a comparison audience of 100,000,000 Accounts Centre accounts (we'll call this audience B), and that there are 800,000 Accounts Centre accounts that are in both audiences. The number 800,000 remains constant no matter which audience is "selected" and which is "comparison". However, the percentage of overlap will change if you switch which is "selected" and which is "comparison". 800,000 means that audience B overlaps with 80% of audience A. However, if audience A becomes the selected audience, that figure changes. Audience A only overlaps with 8% of audience B. In practice, this means that the overlap between the two audiences is more likely to cause delivery problems for ad sets targeting audience A than ad sets targeting audience B.