Mobile Measurement Partner (MMP)

Mobile attribution is the process of connecting app installs and in-app actions to specific marketing campaigns, ads, or channels that drove them. It enables marketers to understand which advertising efforts deliver results, optimize ad spend across channels, and make data-driven decisions about user acquisition strategies.

SKAdNetwork (SKAN) is Apple's privacy-preserving attribution framework for measuring the effectiveness of advertising campaigns that drive app installs on iOS. Introduced as an alternative to IDFA-based tracking after ATT severely limited user-level tracking, SKAN provides aggregated, anonymized attribution data directly from Apple's servers — without revealing any information about individual users. Under SKAN, when a user clicks an ad and installs an app, Apple validates the install and sends an attribution postback to the ad network after a delay, containing limited information: the ad network ID, campaign ID, and a conversion value set by the developer. The conversion value (initially 6 bits allowing 64 possible values, expanded in SKAN 4.0 with coarse and fine values) is the developer's only mechanism for encoding post-install user behavior into the attribution signal. This means developers must carefully decide which events to encode — such as whether the user started a trial, made a purchase, or reached an engagement threshold — within a constrained time window. SKAN's design prioritizes user privacy through delayed, aggregated reporting with built-in noise, which makes campaign-level optimization significantly more challenging than traditional attribution methods.

A postback (also called a server-to-server callback or S2S callback) is a server-side communication mechanism used to send conversion data from one system to another without relying on client-side tracking. In mobile attribution, postbacks are the primary method by which Mobile Measurement Partners (MMPs) communicate install and event data back to ad networks. When a user installs an app and the MMP attributes that install to a specific campaign, the MMP fires a postback to the relevant ad network containing the attribution details (campaign ID, ad group, creative, conversion timestamp, etc.). This enables the ad network to optimize its algorithms and allows the advertiser to measure performance. In the SKAdNetwork framework, Apple sends postbacks directly from the device to the ad network, bypassing the MMP entirely for initial attribution. Postbacks are also used in web-to-app flows to communicate web conversion events to advertising platforms — for example, when a user completes a subscription purchase on a web checkout page, a server-side postback can be sent to Meta or Google to feed their optimization algorithms with conversion signals.

Event-based attribution is a method of crediting marketing channels or campaigns based on specific post-install events that a user completes, rather than attributing value solely at the point of install. While traditional mobile attribution focuses on which ad or campaign drove the app install, event-based attribution goes deeper by tracking downstream actions like free trial starts, subscription purchases, in-app purchases, or reaching a specific engagement milestone. This approach is particularly valuable in the post-ATT landscape where install-level attribution data is limited. By shifting focus to post-install events, marketers can better evaluate which channels drive high-quality users who actually convert and generate revenue, rather than just volume of installs. Event-based attribution works in tandem with SKAdNetwork's conversion value framework, where developers can encode specific post-install events into the limited conversion value bits available. It also enables more sophisticated optimization of ad campaigns, since platforms like Meta and Google can optimize toward deeper funnel events when provided with conversion signals tied to revenue-generating actions.

A lookback window (also called an attribution window) is the defined time period during which an ad click or impression can be credited for a subsequent app install or conversion event. If a user clicks an ad but doesn't install the app until after the lookback window has expired, the install is classified as organic rather than attributed to the campaign. Standard lookback windows vary by platform and ad network: click-through attribution windows are typically 7–30 days, while view-through (impression-based) attribution windows are usually 1–24 hours. The length of the lookback window significantly affects how marketing performance is measured. Shorter windows produce more conservative attribution (fewer attributed installs) but higher confidence that the ad actually influenced the decision. Longer windows capture more potential influence but increase the risk of over-crediting ads for installs that would have happened organically. In the SKAdNetwork framework, Apple uses fixed attribution windows — initially 24 hours for click-through and not supported for view-through — which is significantly more restrictive than the industry standard and has forced marketers to rethink how they measure campaign performance on iOS.