iOS 15 Prewarming

[jandrewlove]

We have a mobile app running on iOS.  Starting September 20th – the launch of iOS 15 – our visits metric began steadily increasing, and continues to this day.  However, most of these increased visits don’t have a page view associated with them.  When I create a segment for “visits with page views >=1”, those visits remain on the trendline that we expect.

iOS 15 introduced a feature called App Prewarming, where the operating system will launch the app and execute the launch sequence up to a certain point then pause it – in an effort make the actual user-initiated startup happen faster.  

We use the Adobe Launch mobile SDK and have it tied to the app’s lifecycle events.  We also use Firebase tied to lifecycle events and it shows the same increase in visits, so what we are seeing is most likely related to this Prewarming ‘feature’.

Has anyone else seen this and what actions have you taken in response?

[EricMatisoff · Accepted solution]

Hi @jandrewlove - Based on some research with our product team that focuses on our mobile SDKs, here's the latest info we have on iOS15 App Prewarming:

According to this document from Apple, the only effect prewarming could have is if the app is executing code before the call to UIApplicationMain, which means it should not be affecting Lifecycle metrics. But if you have specific anomalies in Lifecycle in iOS 15, please do submit an issue to customer care and we can look into it further.