Crowd anonymity

How it works

A postback is anonymous only if it could describe many different people. So the system relates the detail to the size of the crowd. Apple says the tier takes into account the crowd size associated with the app or domain displaying the ad, the advertised app, the country of the install and the source identifier the ad network provides.^[1] Apple's documentation page gives no thresholds.

Apple's documentation puts it this way: to maintain users' privacy and ensure crowd anonymity, the device may limit the data that SKAdNetwork sends in postbacks, and Apple determines a postback data tier that it assigns to each app download.^[1] The tier has visible effects:

• In lower tiers, the system sends the coarse conversion value in place of the fine-grained one.^[1]
• At Tier 0, the system sends only the first postback.^[1]

Apple assigns the tier.^[1] You see its result in what each postback contains.

When it matters

It matters most to small advertisers. A campaign with few installs can return postbacks with less in them, which can look like broken tracking when it is the privacy rule doing its job. Before you conclude that a campaign brought low-quality users, check whether its postbacks carried the fine-grained value or only the coarse one.

The practical response is to concentrate volume. Fewer, larger campaigns give each one a bigger crowd than many small ones do.

How it relates to attribution

Crowd anonymity decides how much of your conversion value mapping you get back. A careful fine-grained mapping is wasted on installs that only return coarse values, so plan the coarse levels first. It also explains why some installs arrive with less detail in your MMP report. The timing side of the same system is in SKAdNetwork postbacks and their three windows.