Guideline 2.1 - App Completeness: App Crashes During Review

Apple is rejecting your app because it crashed or exhibited a fatal error during their review. This is one of the most frustrating rejection types because the crash may not be reproducible on your own devices. Apple tests on specific hardware and OS versions that may differ from your development environment, and they sometimes have intermittent network conditions or different locale settings. The root cause is almost always one of: (1) a race condition or timing issue that surfaces on slower or different hardware, (2) a nil/null dereference triggered by a code path the reviewer hit that you didn't test, (3) a server-side issue where your API was down or rate-limited during review, or (4) a crash related to the reviewer's specific device, locale, or accessibility settings. Apple's reviewers test on physical devices, not simulators. They also tend to test quickly, which means rapid navigation and state transitions that may expose bugs you've never seen. If they provide a crash log, it's gold — but often the email just says 'the app crashed' without specifics, and you'll need to check your own crash reporting.