When people interact with your Facebook ads or Instagram ads, they can take a variety of actions such as watching your video, visiting your website, or purchasing your product. Each of these actions is recorded. When your ad leads to a conversion, Facebook will attribute (credit) the ad in Ads Manager. It’s important to have this data to see how well your campaigns and ads are doing and determine if you’re reaching your targets.
The number of days between when someone viewed or clicked your ad and then took action on your website is referred to as an “attribution window.” The default Facebook attribution window settings show actions taken within 1 day of viewing your ad and within 28 days of clicking your ad.