How to measure iOS app start-up times

Short app load times are imperative to a good user experience.

The most important baseline measurement is the cold start time — the time it takes for your app to load before iOS calls main(), before any app data is cached in memory. A good load time is around 400ms.

To do this:

1. Go to Xcode’s scheme navigator and select your app target.
2. Press Edit Scheme….
3. Select the Run action tab.
4. Select the Arguments tab.
5. Under the Environment variables section, press the + button.
6. In the Name column, add DYLD_PRINT_STATISTICS.
7. In the Value column, add 1.

Edit scheme

Now, when you run your build, the console panel with show the app’s pre-main times.

Typical console output

Make sure you measure this, before you ship.