lockWindow

What is lockWindow?

lockWindow is a feature introduced in Apple's SKAdNetwork (SKAN) 4 that allows advertisers to manually finalize and lock a conversion value before the designated conversion window closes. It applies to any of the three SKAN 4 conversion windows, enabling earlier postback dispatch without waiting for the full window duration to expire. By calling lockWindow, the system immediately begins preparing the postback and disregards any subsequent conversion value updates within that window.

How it works

SKAN 4 introduces three sequential conversion windows: days 0 to 2 (window 1), days 3 to 7 (window 2), and days 8 to 35 (window 3). Each window can produce a postback, and apps can update conversion values throughout each window's duration.

Default Behavior Without lockWindow

By default, the system waits until the full conversion window closes before generating the postback. Once the window closes, the postback is dispatched after a random delay: 24 to 48 hours for the first postback, and 24 to 144 hours for the second and third postbacks. This means advertisers may wait several days before receiving conversion data.

Behavior With lockWindow

When an app calls the lockWindow function during an active conversion window, the system immediately finalizes the conversion value at that moment. No further updates to the conversion value within the same window are accepted or reflected in the postback. The postback is then queued and sent following the same random delay periods: 24 to 48 hours for the first postback and 24 to 144 hours for the second and third postbacks.

Critically, calling lockWindow does not guarantee the postback arrives immediately. The random delay still applies after the window is locked. However, because the window closes earlier than it would by default, the overall time to receiving the postback can be meaningfully shorter.

Scope of Application

lockWindow can be applied independently to any one, two, or all three conversion windows. This gives advertisers granular control: for example, an app might lock window 1 early to capture install-day events quickly, while allowing windows 2 and 3 to run their full duration for richer post-install behavioral data.

Why it matters

Timely conversion data is critical for campaign optimization. In standard SKAN 4 flows, the third conversion window alone can keep advertisers waiting over five weeks from install before the final postback arrives. This lag delays bid adjustments, creative decisions, and budget reallocations.

lockWindow reduces this latency by allowing advertisers to signal that a user's most meaningful conversion activity has already occurred within a window. If an app's key conversion event, such as a first purchase or account registration, consistently happens within the first two days, locking window 1 early ensures that data reaches ad networks faster, accelerating the feedback loop for algorithmic bidding.

The trade-off is data completeness. Locking a window early means any higher-value conversion events that occur later in the same window are not captured in that postback. Advertisers must balance speed against the richness of conversion signals. For campaigns where rapid iteration matters more than capturing late-window events, lockWindow provides a meaningful operational advantage. Airbridge supports SKAN 4 postback handling, enabling teams to align their lockWindow strategy with their broader measurement configuration.

How to set up lockWindow in SKAN 4

Setting up lockWindow requires coordination between your app's SKAdNetwork integration, your conversion value schema, and your MMP configuration.

Step 1: Map your conversion events by timing. Audit which in-app events typically occur within each conversion window. If your primary conversion event happens reliably within the first two days, window 1 is a strong candidate for early locking.

Step 2: Define your conversion value schema. Before implementing lockWindow, finalize what conversion value you want to lock. Because no updates are accepted after lockWindow is called within that window, the value must represent the most complete picture of user activity you need at that point.

Step 3: Implement the lockWindow API call. In your app's SKAdNetwork integration, call the updatePostbackConversionValue(_:coarseValue:lockWindow:) method with the lockWindow parameter set to true. This is available in iOS 16.1 and later under StoreKit. Ensure your SDK or MMP integration supports passing this parameter.

Step 4: Configure your MMP to handle early postbacks. Because postbacks from locked windows may arrive before the full window would have closed, verify that your MMP, such as Airbridge, is configured to ingest and attribute these postbacks correctly without treating them as anomalies.

Step 5: Monitor postback timing in reporting. Track the actual time-to-postback across windows to validate whether lockWindow is delivering the expected latency reduction. Compare campaign performance data timeliness before and after implementation to assess the practical impact on your optimization cycles.

Step 6: Iterate per window independently. Evaluate lockWindow usage for each window separately. A strategy that locks window 1 aggressively may benefit paid user acquisition campaigns focused on early conversions, while leaving window 3 open may suit retargeting campaigns analyzing longer-term engagement.

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