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#  Learn about app start, app-in-foreground, and app-in-background performance
data (Apple & Android apps)

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preferences.

iOS+  Android

Performance Monitoring uses _traces_ to collect data about monitored processes
in your app. A trace is a report that contains data captured between two
points in time in your app.

For Apple and Android apps, Performance Monitoring _automatically_ collects
several traces related to app lifecycle. All these traces are like timers
because they measure the time it takes for the process to run (the
"duration").

  * App start trace  — A trace that measures the time between when the user opens the app and when the app is responsive 

  * App-in-foreground trace  — A trace that measures the time when the app is running in the foreground and available to the user 

  * App-in-background trace  — A trace that measures the time when the app is running in the background 

Since these traces only collect the metric "duration", they are sometimes
called "Duration traces".

You can view data from these traces in the _Custom traces_ subtab of the
traces table, which is at the bottom of the _Performance_ dashboard (learn
more about  using the console  later on this page).

These out-of-the-box traces get you started with monitoring your app, but to
learn about the p