What is Crowd Anonymity on SKAdNetwork?

Apple’s way of ensuring users DON’T stand out from the crowd

In October, SKAdNetwork v4.0 was released alongside iOS 16.1. This new version expands the amount of information marketers may glean through attribution while maintaining Apple’s privacy-protecting policies. While Apple has not released the specifics of its privacy threshold counts and may never do so, the current release of v4.0 provides marketers and advertisers with a bit more information with which to adjust their marketing plans.

Now, let’s get into the meat and potatoes.

What is crowd anonymity?

Apple previously defined “crowd anonymity” levels based on attribution volume in June: low, medium, and high. However, following its release, Apple built on the Tiers 1-3 concept, as seen below, introducing the concept of Tier 0 for a total of 4 tiers.

Crowd anonymity is too low in Tier 0, resulting in massive data redaction or no postbacks at all. Essentially, the larger the crowd, the more anonymous each individual member becomes. As crowd anonymity increases with each tier, more granular data becomes available within the conversion postbacks Apple sends to ad networks and advertisers. The most granular data is only available at the highest crowd anonymity tier to ensure that SKAdNetwork remains truly anonymous – preventing any data points from being tied back to an individual user or device.

*Note that Apple still does not precisely provide the thresholds for each tier, only that with more attributed volume, each tier is reached, and more data is shared.

How Apple categorizes app downloads within tiers

Apple provided insight into the categorization of app downloads within tiers. The placement is determined in accordance with 3 main factors as described below.

1	2	3
The crowd size associated with the app or domain displaying the ad	The advertised app	The hierarchical source identifier the ad network provides

The crowd anonymity tier reached has bearing on the following conversion postback elements:

Whether the postback gets sent
What conversion value (if any) gets included: fine-grained, coarse-grained, or none
How many digits of the source identifier are disclosed: all digits, 3 digits, or only last 2 digits
Whether the source app ID is included

Hierarchical conversion values

Inherently linked to crowd anonymity are the two sets of hierarchical conversion values Apple will be incorporating in SKAdNetwork v4.0: coarse-grained and fine-grained.

Coarse-grained: This value can be set to one of three possible values and is included in postbacks when the crowd anonymity tier restricts the fine-grained conversion value. When the attribution volume is too low to share the conversion value, the coarse value will be included in its place, and at the lowest tier – even the coarse value is excluded. Note that the coarse value and conversion value are mutually exclusive; the coarse value cannot be used in tandem with the conversion value in the conversion model.

Fine-grained: This value is used for reporting post-install engagement from the advertised app. The coarse-grained value passes the current SKAdNetwork conversion value, which can be any value between 0-63. It’s only available in the first conversion window range at higher crowd anonymity tiers.

The following pivot table showcases how crowd anonymity impacts the conversion value available across the three different conversion windows (0-2 days, 3-7 days, and 8-35 days).

Note that at the lowest tier, absolutely no conversion value (fine or coarse) is available. Additionally, the fine-grained value is only available in the conversion postback for the 0-2 day callback window.

Campaign identifier field –> source identifier

SKAdNetwork 4.0 replaces the 2-digit campaign identifier field from the ad impression with a new 4-digit ‘source identifier’ field. This field should be considered a ‘conversion value’ equivalent to the ad impression. Certain digits become available as higher tiers of crowd anonymity are reached. Similar to conversion values, these four digits could be used to represent different data. However, since Apple obscures certain digits based on the level of crowd anonymity, each digit should represent something meaningful and discernible independently. Apple used the following model as an example:

Digit #4 = Ad placement bucket
Digit #3 = Date bucket
Digit #1,2 = Campaign ID

The diagrams below showcase how the crowd anonymity tier impacts the source identifier and source app ID across all three conversion window ranges.

Note that for source app ID this value is ONLY available in the first postback when the crowd anonymity is at Tier 3.

Less is definitely not more with SKAN v4

The gist of crowd anonymity is that advertisers are able to receive data at a level that corresponds with the number of installs their campaigns generate while still affording privacy to consumers. As campaigns meet higher privacy thresholds, more attribution insights will become available. For this reason, advertisers won’t want to spread their spend thin on iOS, but rather will want to spend adequately with each partner across each campaign to reach data significance in order to unlock meaningful and actionable insights for optimizations.

SKAdNetwork had only one universal privacy threshold prior to v4.0 – a one-size-fits-all approach. This new multi-tiered methodology, combined with the addition of coarse- and fine-grained conversion values over three conversion postback windows (as opposed to the current 1), should genuinely improve performance insights for marketers to make decisions on.