SKAdNetwork 4.0 expanded Apple’s privacy-preserving app attribution when it arrived with iOS 16.1. This March 2023 article looks at that release: what changed from earlier SKAN versions, what advertisers could measure, and where privacy limits still applied. SKAN does not reveal a user’s advertising identifier in its postbacks. Its extra reporting detail can support campaign decisions, but it does not restore unrestricted device-level tracking or guarantee better return on ad spend.
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What is SKAN?
SKAdNetwork (SKAN) is Apple’s privacy-preserving app-install attribution framework, introduced in 2018. Devices send signed postbacks with attribution information rather than user or device identifiers; advertisers can use them for campaign reporting. The information available depends on the framework version and Apple’s privacy rules. The main versions covered by this article are: 
Timeline correction: the original illustration labels SKAN 2.2 as 2020. SKAN 2.2 arrived with iOS 14.5 in April 2021. The illustration is retained as historical artwork; use the corrected version descriptions below.
SKAN 1.0
The original SKAN version was available from iOS 11.3. Its install-validation postback included attribution fields such as the ad network, advertised app and campaign identifier. Conversion values were added in SKAN 2.0, not in this first version.
SKAN 2.0
SKAN 2.0, available with iOS 14, added conversion values for post-install engagement. Its postback also added the version number, source app ID and redownload flag. The redownload flag indicates a download of an app that the person had previously obtained.
SKAN 2.2
SKAN 2.2, available with iOS 14.5, added view-through ads and the fidelity-type field distinguishing them from StoreKit-rendered ads. Conversion values already existed in SKAN 2.0. Attributable Safari web ads were a later addition in SKAN 4.0.
SKAN 3.0
SKAN 3.0, available with iOS 14.6, added postbacks for qualifying impressions that did not win attribution. The winning network receives did-win=true, while up to five other qualifying networks can receive did-win=false. It did not introduce native ad-group or creative-ID fields, or the three conversion windows later added in SKAN 4.0.
SKAN 4.0
SKAN 4.0 was the release this article examined in March 2023. Available with iOS 16.1, it added hierarchical source identifiers, coarse conversion values, up to three winning postbacks and attributable ads on Safari web pages. Apple’s SKAN 4 release notes describe the integration requirements.
The problems with past versions of SKAN
Past versions had limitations and drawbacks that posed challenges for advertisers and app developers.
Limited Attribution Windows
Attribution eligibility and post-install observation are different windows. StoreKit-rendered ad interactions can have a 30-day install window, while view-through impressions have a 24-hour install window. Earlier SKAN versions used a single winning postback and a conversion-update timer; they were not universally limited to installs occurring within 24 hours.
Limited Campaign Attribution
Earlier SKAN versions could report multiple campaigns. Their campaign identifier had a range of 0 to 99, which limited the combinations an ad network could encode. SKAN 4.0 expanded that field into a hierarchical source identifier; it did not remove a one-campaign-per-app restriction.
Incomplete Conversion Data
From SKAN 2.0, apps could encode post-install engagement in a conversion value. The limitation was the small, privacy-limited value and a single winning postback, rather than a total absence of post-install data. SKAN 4.0 added later conversion windows, but these still do not provide a complete user history or lifetime value.
What does SKAN 4 change?
Three changes were especially useful for measurement planning: the hierarchical source identifier, more conversion-value options and support for attributable web ads.
Campaign Measurement
- SKAN 4.0 gives ad networks more ways to encode campaign information while keeping the returned detail subject to privacy limits.
- SKAN 3.0 used campaign IDs from 0 to 99. In SKAN 4.0, an ad network can set a four-digit source identifier with up to 10,000 combinations and choose what its digits mean. A winning postback returns only two, three or four digits, depending on privacy conditions. Location, placement or creative can be part of the network’s encoding; they are not automatically available as separate fields.
Conversion Values
SKAN 4.0 lets apps provide a fine value from 0 to 63 and a coarse value of low, medium or high. A postback can return one value type, subject to privacy conditions. Fine detail is available only in the first conversion window; the later windows can return coarse values. These are encoded engagement signals, not identifiable user profiles.
Web Support
SKAN 4.0 supports eligible ad links initiated in Safari, allowing an ad network to attribute the resulting App Store install through the same privacy-preserving postback system. This requires the network’s signed impression setup. It does not reveal unrestricted browser behavior or automatically connect every web and app interaction.
What does SKAN 4 mean for advertisers?
For advertisers, these changes create more measurement options, with several limits to keep in the plan.
- First, separate the existing view-through feature from the new SKAN 4.0 features. View-through ads arrived in SKAN 2.2. The additional conversion windows in SKAN 4.0 allow eligible winning attributions to report more post-install engagement, subject to the app implementation and privacy tier.
- Second, verify signed postbacks and reconcile them with campaign and product reporting. A valid attribution postback is useful evidence that an eligible ad received credit. It does not, by itself, establish incremental lift, eliminate fraud or prove that a campaign is profitable.
SKAN 4.0 offered more reporting detail without returning user identifiers. The practical question was whether an app, its measurement partner and its ad networks supported the required implementation, and whether enough useful data was returned to inform decisions. Advertisers still needed mature cohort reporting and, where feasible, incrementality tests before treating attributed results as evidence for more spend.
How to get SKAN 4.0 to work for your app
At the time of this March 2023 article, Admiral was working on SKAN 4.0 setups for clients. Implementation requires coordination between the app, measurement partner and ad networks, followed by tests of the conversion mapping and postback handling. The original article listed Pablo Perez, then Performance Marketing Director at Admiral Media, as its SKAN contact. For a current setup, confirm the present SDK, network support and measurement owner before changing a live integration.
