App Starts

The App Starts dashboard in Sentry Dashboards shows an overview of the amount of time it takes for your application to complete cold and warm starts. It helps you identify slow or regressed screens and gives additional information so you can better understand the factors contributing to the slowness of your application start times.

Minimum SDK Requirements:

For Android:

• >=7.4.0 for automatic instrumentation of app start spans and app start profiling
• Performance-V2 feature flag (<8.0.0) and App Start Profiling must also be enabled in the SDK, e.g.:

import io.sentry.android.core.SentryAndroid;

SentryAndroid.init(this, options -> {
  options.setEnablePerformanceV2(true);
  options.setEnableAppStartProfiling(true);
});

import io.sentry.android.core.SentryAndroid;

SentryAndroid.init(this, options -> {
  options.setEnablePerformanceV2(true);
  options.setEnableAppStartProfiling(true);
});

import io.sentry.android.core.SentryAndroid

SentryAndroid.init(this) { options ->
  options.enablePerformanceV2 = true
  options.enableAppStartProfiling = true;
}

<manifest>
    <application>
        <meta-data
      android:name="io.sentry.performance-v2.enable"
      android:value="true"
    />
        <meta-data
      android:name="io.sentry.traces.profiling.enable-app-start"
      android:value="true"
    />
    </application>
</manifest>

For iOS:

• >=7.2.0 for automatic instrumentation of app start spans
• >=8.21.0 for app start profiling

For React Native:

• >=5.24.0 for automatic instrumentation of app start spans

By default, the App Starts dashboard displays metrics for the two releases with the highest screen counts for the time range you've selected. To choose a different set of releases to compare, use the "release selector" at the top of the dashboard. To change the app start type (cold or warm), use the "App Start" selector at the top of the dashboard.

The charts display the following metrics (using cold starts as an example):

• Average Cold Start
  • The overall time it takes your application to start, compared by release.
• Cold Start Device Distribution
  • The average cold start time grouped by device class (high, medium, low, or unknown).

Reasons Why You Might Not Be Seeing Any Data:

• You don't have any transactions with op ui.load
• Your SDKs don't meet the minimum SDK requirements

The table at the bottom shows spans that have changed from one release to the next and allows you to filter for specific span operations and device classes. Being able to narrow down to specific event samples helps debug slow starts.

Clicking the "By Event" toggle in the top right corner of this table will show you events split by release and you'll be able to see overall changes in start times between the two releases you've selected.

The following table describes the span operations that are surfaced in the spans table:

Cold and Warm Starts

Both Android and iOS distinguish between cold and warm starts, but the exact definitions and measurement approaches differ between platforms:

For full details, see the Android app start and iOS app start SDK documentation.

Headless App Starts

A headless app start occurs when your Android application's process is created without launching a visible Activity. This can happen when the app is started by a broadcast receiver, a content provider, or a background service — the process initializes but no UI is displayed to the user.

By default, Sentry only tracks app starts that result in a foreground Activity being displayed. With headless app start tracking, Sentry can also capture these non-UI process launches, giving you visibility into background initialization performance.

Headless app start tracking requires standalone app start tracing to be enabled in your Android SDK configuration:

<application>
    <meta-data
    android:name="io.sentry.standalone-app-start-tracing.enable"
    android:value="true"
  />
</application>

<application>
    <meta-data
    android:name="io.sentry.standalone-app-start-tracing.enable"
    android:value="true"
  />
</application>

Span Detail View

Clicking on a span description opens up the Traces page, where you can see sampled spans.

In the table, you'll see a list of sampled spans. Click into one to get a waterfall view of the span.