Glossary

lockWindow

lockWindow is a feature in Apple’s SKAdNetwork version 4 that allows app developers and advertisers to end a measurement window early. When a window is locked, Apple finalizes the conversion value and prepares the postback, instead of waiting for the full default measurement period to run.

SKAN 4 introduced three conversion windows, which together cover up to thirty five days after a user first opens an app. With lockWindow, teams can choose to finalize results earlier within any of these windows, allowing postbacks to arrive sooner and accelerating optimization cycles.

How SKAN 4 Measurement Windows Work

SKAN 4 tracks post install behavior in three windows:

  • First window covers day zero to day two
  • Second window covers day three to day seven
  • Third window covers day eight to day thirty five

Apps can update the conversion value inside each window. When a window ends, the value freezes. Apple then adds a random delay before sending a postback. The first postback has a shorter delay range than the second and third.

Without lockWindow, each window runs its full duration. With lockWindow, you can choose to stop the window early and lock the value as soon as you believe you have collected the key data for that stage.


How lockWindow Works

Think of lockWindow as a manual close button for a measurement period. When you trigger it:

  • SKAN stops listening for value updates for that window
  • The current conversion value becomes final for that postback
  • The random delay period begins immediately

The earlier you lock, the faster you receive the postback. However, any events that happen after locking inside that same window will be ignored.

The random delay still applies. lockWindow does not guarantee instant delivery, it simply starts the delay sooner.


Why lockWindow Matters

SKAN postbacks arrive with privacy based delays. In fast moving performance environments, early insight can help you:

  • Test creative and bidding strategies faster
  • Optimize spend with quicker signals
  • Reduce wasted budget on underperforming cohorts
  • Increase agility when launching campaigns or iterating on product flows

At the same time, locking early means collecting less behavioral data. It is a trade off between speed and depth.


When to Use lockWindow

Use lockWindow when most valuable early events happen quickly after install. For example:

  • You run a campaign for a casual mobile game and most meaningful events like tutorial completion and first purchase occur within the first day.
  • You want rapid creative testing and do not need full window data to decide.

Most teams consider using lockWindow only in the first conversion window. Later windows often contain slower signals like subscription decisions or return engagement patterns, and cutting them short risks losing important insight.


When Not to Use lockWindow

Avoid locking too early when:

  • Key value events occur gradually across the window
  • You are measuring deeper funnel events like trial starts or long term engagement
  • You rely on a full distribution of conversion values for predictive models
  • You are analyzing lifetime value or retention trends across the post install period

If you are unsure, start without locking and observe how quickly meaningful events cluster. Adjust with evidence.


Practical Tips

  • Map your day zero to day seven and day eight to day thirty five behaviors
  • Plot when users complete onboarding, activate key features, or make first purchases
  • Use cohort studies to find the typical time to meaningful events
  • Experiment with locking only after a threshold of high value events is reached
  • Track campaign performance both with and without locking to validate lift

The goal is to lock only after enough data has been gathered to make reliable performance calls.


FAQs

Does lockWindow send the postback instantly

No. It finalizes the value and starts the random delay earlier, but the delay still applies.

Can I lock more than one window

Yes. You may lock each window independently.

What happens to events after I lock

They are ignored for that window. Future windows still run normally unless you lock them too.

Is lockWindow required

No. It is optional. It is a tool for faster feedback when appropriate.

Should I always lock the first window

Not always. Only do so if your most meaningful conversion events reliably occur early and your team benefits from faster feedback.

Does locking affect privacy thresholds

lockWindow does not bypass SKAN privacy rules. Crowd anonymity thresholds and coarse or fine value eligibility still apply.


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