Mobile Vitals

Mobile Vitals are a set of metrics that measure how fast your app starts and the number of slow and frozen frames your users experience. Each metric provides insights into the overall performance of your mobile application and gives you the details you need to not only prioritize critical performance issues, but to trace issues down to the root cause to solve them faster.

Mobile Vitals are summarized in several graphs on the Performance page in sentry.io in the "Mobile" tab.

Performance page in Sentry with Mobile Vitals.

App Start

App start metrics track how long your mobile application takes to launch. For this, Sentry measures cold starts and warm starts.

The definitions of cold start and warm start change slightly depending on the operating system. On iOS, Apple recommends your app take at most 400ms to render the first frame. On Android, the Google Play console warns you when a cold start takes longer than five seconds or a warm start longer than two seconds. For definitions by operating system, check out the corresponding SDK docs:

In the example below, the detail view of a transaction displays the warm start measurement in the right sidebar.

The event detail of a transaction with a warm start measurement.

While the SDKs differentiate between a cold and a warm start, they don't track hot starts or resumes.

Slow and Frozen Frames

To track the responsiveness of the user interface, Sentry measures slow frames and frozen frames. Typically, a phone or tablet renders 60 frames per second (fps). At 60 fps, every frame has 16 or 16.67 ms to render.

  • Slow Frames: Using 60 fps, slow frames are frames that take more than 16 ms (Android) or 16.67 ms (iOS) to render.
  • Frozen Frames: Frozen frames are frames that take longer than 700 ms to render.

For Apple, the frame rate can be higher, especially as 120 fps displays are becoming more popular. For these apps, Sentry detects the frame rate and adjusts the slow frame calculation accordingly.

In the example below, the detail view of the transaction displays the slow, frozen, and total frames in an iOS application:

The event detail of a transaction with slow and frozen frames measurements.

You can track slow and frozen frames for:

Help improve this content
Our documentation is open source and available on GitHub. Your contributions are welcome, whether fixing a typo (drat!) to suggesting an update ("yeah, this would be better").