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SKAdNetwork is a privacy-centric interface operated by Apple. It helps ad networks and advertisers measure their ad activity (such as impressions, clicks, and app installs) on an aggregated level, without accessing individual user data.
First introduced by Apple back in 2018, SKAdNetwork (often shortened to SKAN) provides attribution data to advertisers on iOS so they can measure and optimize campaigns. Because it does this on an aggregated level, without revealing any user-level or device-specific data, it offers an accurate yet privacy-preserving source of campaign insights.
Did you know?
SKAd Network is short for StoreKit Ad Network. The StoreKit is a framework that enables various features and functionalities for iOS apps, including transactions, in-app purchases, and ad attribution.
Before we launch into the mechanics, let’s take a look at the four main players involved, each having specific roles and responsibilities:
There are two types of engagements that SKAdNetwork registers:
A postback is where an attribution provider (in this case, SKAd Network) sends data back to the ad network and advertiser on user behavior — for example, whether they clicked on an ad or downloaded an app. This provides vital feedback that enables advertisers to optimize their campaigns.
Unlike standard postbacks, SKAdNetwork postbacks are not immediately sent to the ad network and advertiser when the app is first launched. In fact, the attribution window (the period in which an ad impression or engagement is considered responsible for a conversion) can be up to 30 days between click and install, depending on the ad type.
SKAdNetwork postbacks are built on a timer mechanism that only sends the postback when the timer runs out. This timer delays the postback by a minimum of 24 hours. Once the timer runs out, the ad network and advertiser receive the postback.
It’s important to note that postbacks don’t contain any device or user data. Together with the timer delay, this ensures that user data remains private by removing the ability to single out a specific user.
If the advertiser is working with an MMP, like AppsFlyer, postbacks will be reported to the MMP via dedicated dashboards and APIs, or as configured by the advertiser.
Compared with previous methods of attribution, SKAdNetwork does present a number of complexities and challenges for advertisers. To name a few:
Fortunately, there are ways to navigate these challenges, so you can continue to measure and predict the value of your acquired users.
The key to unlocking value from SKAdNetwork is to understand Apple’s unique conversion value mechanism.
Conversion values are configured by app developers to measure post-install activity, and tie it back to the install. A single conversion value is included in the one-time postback that Apple sends to the ad network and advertiser.
As a result, the information in this conversion value is all you get on a user’s post-install activity (assuming they didn’t consent to “tracking”), making it extremely important. After all, in a freemium world, optimization is driven by post-install data.
Starting with SKAN 4.0, there are two types of conversion values:
As long as you properly map your conversion values based on your internal logic, these values can be used in any way you want. They’re yours to control and assign to the KPIs that are most valuable to you.
The 64 fine-grained values and 3 coarse-grained values, each with their own unique decoding configured by the app developer or advertiser, are then attributed to the source of the install, enabling campaign measurement and optimization.
Different approaches work for different app types. For example, data from AppsFlyer’s Conversion Studio shows that gaming apps are laser-focused on revenue – as such, it’s a model that’s being involved in most conversion value schemes. On the non-gaming side, in-app activity is the most configured option.
Learn more here about how to make the most of conversion values, including benchmarks on activity window timer, and optimal usage of the 64-combination capacity.
On October 24, 2022, Apple released the next version of SKAdNetwork (4.0). This introduced significant changes that allow advertisers and ad networks to measure more while maintaining user privacy.
SKAdNetwork 4.0 enables advertisers to receive up to three postbacks, each based on a specific activity window (0-2 days, 3-7 days, and 8-35 days). This allows advertisers to understand how users engage with their app over time.
The first postback is sent within 24-48 hours as before. However, the length of the timer increases for the second and third postbacks, which are sent after 24-144 hours.
Although it’s important to note that these three postbacks cannot be connected and tied to a specific user, advertisers are still able to count unique event occurrences.
Although each postback is based on a limited activity window, SKAN 4.0 also introduces a new ability called LockWindow, which allows app developers to finalize the conversion value and lock the measurement window in order to receive postbacks sooner. For example, app developers can lock the window of the second postback anywhere between day 3 and day 7.
Crowd anonymity is a new term that Apple uses to describe the privacy-preserving way in which SKAN delivers attribution data. In short: the more installs you get, the more data you get.
To maintain user privacy, Apple limits the data that SKAN shares in postbacks. Postback data tiers are based on the conversion-volume of the campaign, like this:
Apple decides which crowd anonymity tier each install belongs to, and shares data accordingly.
For example, for ads in tier 0, the postback will not include a conversion value (null). Whereas for ads in tier 1, the first postback will include only a coarse conversion value and a two-digit source identifier. However, for ads in tiers 2 or 3, the first postback will include a fine-grained conversion value and a two to four-digit source identifier. The second and third postbacks will only be shared if the crowd anonymity tier is above 0, and will include only a coarse conversion value and a two-digit source identifier.
Here’s a summary:
In earlier versions of SKAdNetwork, postbacks included a conversion value only in cases where Apple’s privacy threshold was met. When crowd anonymity is low, Apple takes extra precautions to protect user privacy by masking the conversion value and source app ID.
SKAdNetwork 4.0 introduces a new set of “coarse-grained” conversion values (in addition to the 64 “fine-grained” values that exist today).
As previously mentioned, coarse-grained conversion values are categorized into three types: low, medium, or high. Advertisers assign these values to signify varying degrees of user engagement, enabling them to obtain partial attribution data when the privacy threshold isn’t reached, particularly at lower levels of crowd anonymity.
Another change introduced in SKAN 4.0, which significantly impacts campaign granularity, involves the source identifier. Apple has taken the step of renaming its campaign identifier field as the source identifier, and along with this change, has expanded its range from two digits (equivalent to 100 options) to four digits (equivalent to 10,000 options).
Although the source identifier is presented as a single number, Apple urges advertisers to interpret it as a sequence of three hierarchical numbers. By adopting this approach, advertisers gain the ability to comprehensively measure various parameters, including factors like ad placement, geographic targeting, creative components, and more.
Coarse-grained values are provided in the 2nd and 3rd postbacks, or in the 1st postback if the privacy threshold is not met; whereas the fine conversion value is included in the 1st postback only.
From SKAN 4.0 onward, Apple is renaming its campaign identifier field to source identifier and increasing its range from 2 digits (representative of 100 options) to 4 digits (representative of 10,000 options).
Although the source identifier is a single number, Apple encourages advertisers to use it as 3 hierarchical numbers — allowing them to measure more parameters, such as ad placement, GEO, creative, and more.
As with hierarchical conversion values, hierarchical source identifiers also adhere to Apple’s privacy threshold — meaning the higher the level of crowd anonymity, the higher the level of provided granularity.
Like hierarchical conversion values, these hierarchical source identifiers also abide by Apple’s privacy threshold. This means that the level of detail provided is directly tied to the level of crowd anonymity, making the system adaptable to diverse privacy requirements.
| Postback 1 | Postbacks 2 &3 | |
| Crowd anonymity tier 0 | Source_identifier with 2 digits only | x |
| Crowd anonymity tier 1 | Source_identifier with 2 digits only Coarse-grained conversion value | Source_identifier with 2 digits only Coarse-grained conversion value |
| Crowd anonymity tier 2 | Source_identifier with 2, 3 or 4 digits fine-grained conversion value | Source_identifier with 2 digits only coarse-grained conversion value |
| Crowd anonymity tier 3 | Source_identifier with 2, 3 or 4 digits fine-grained conversion valuesource_app_ID/ source_domain | Source_identifier with 2 digits only coarse-grained conversion value |
Previously, advertisers could only measure app-to-app flows, but web-to-app was not supported. In SKAN 4.0, Apple supports web-to-app attribution for Safari, enabling advertisers to measure campaign performance across multiple channels.
Find out more about SKAN 4.0 changes and building your strategy
Here are a few steps to ensure your business is SKAdNetwork-ready:
SKAdNetwork, introduced by Apple, offers a privacy-compliant way to provide advertisers with attribution data for iOS campaigns. By aggregating the data, it protects user and device-specific details while enabling campaign optimization.
SKAdNetwork (SKAN) stands for StoreKit Ad Network. The StoreKit framework, on which it’s based, supports multiple functionalities for iOS apps, encompassing transactions, in-app purchases, as well as ad attribution.
When an ad is displayed, SKAdNetwork registers its view and, if the user engages with the ad and downloads the advertised app within a certain time window, that download will be attributed to the ad network. Postbacks are sent to both the ad network and advertiser, providing behavioral data without compromising user privacy.
SKAdNetwork presents a number of challenges, including limited ROI/LTV measurement, data granularity, postback delays, ad fraud risk, and lack of re-engagement support. Understanding Apple’s conversion value mechanism and working with an MMP can mitigate these issues.
SKAdNetwork 4.0 introduces up to three postbacks based on distinct timeframes. It also offers a LockWindow feature for quicker postback reception, crowd anonymity for privacy-preserving data sharing, and an expanded source identifier range for detailed campaign measurement.
Advertisers should aggregate and validate SKAdNetwork data, and enrich it with additional metrics for comprehensive analysis. They should also ensure seamless integration with mobile attribution solutions, and define conversion events for dynamic in-app activity measurement.
As the mobile advertising industry continues to adapt to a privacy-centric reality, the ability to measure, attribute, and optimize will continue to improve. Better models, increased usage of predictive analytics, acquired expertise in SKAN, and innovation across the ecosystem have all driven improvements in measurability.
As an advertiser, you should:
