This guide applies to all frameworks that create or generate iOS applications.

When debugging the iOS version of the app with Smartlook, a warning is encountered which title reads:

The warning is harmless, and is caused by Smartlook’s capturing screen on the background. The alternative (capturing the screenshot on the main thread) may cause glitches of the app UI – so implementing it this way and having this warning is a necessary trade-off to enable seamless recording functionality.

This warning also might be accompanied by a short freeze of the app during debugging. This freeze does not happen in production builds, and is caused by the `Main Thread Checker` Xcode diagnostic option.

This option can be switched off in the respective run scheme diagnostic options, see "Detect Improper UI Updates on Background Threads" section of the "[Diagnosing Memory, Thread, and Crash Issues Early](🔗)."