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App Performance


5 Mobile App Performance Metrics to Watch and Why

App stability is crucial, but it’s only one measure of app quality. Crashes can't tell you everything—there are many other reasons behind user frustration and a poor app experience. While crashes tend to quickly alienate users, slow performance is the less-obvious drag on long-term app usage. It's essential for developers to monitor how long a user waits at launch, between screen transitions, and after performing a request. In this post, we'll highlight 5 often-overlooked metrics for app performance.

Key Mobile App Performance Metrics

App launch

App launches drive first impressions of mobile app quality. To the end user, launch speed is a first indicator of the overall quality of your app and sets expectations for performance. App launches remain important throughout the entire user lifetime, as repeat slow launches impact long-term retention. To get the full picture, monitor all launch types and first landing screen loading times. 


  • Cold launch: 2–4 seconds 
  • Warm launch: 2-3 seconds
  • Hot launch: 1–1.5 seconds

UI responsiveness

Don’t leave them hanging—users are conditioned to expect quick and accessible experiences, and they may abandon your app or view your brand unfavorably if they encounter slow or hanging UI performance. You can assess UI hangs by comparing your app’s delay in responding to a user input to the total amount of time they spend on a certain screen. This metric is frequently ignored, but has a major impact on user experience.

  • Target: <100ms
  • Hang: 250ms

Network performance

Network requests contribute heavily to app speed and responsiveness. What a user may perceive as a hang or error may actually be a slow or failed network call. Many mobile teams monitor server-side performance, but they’re only capturing half of the user experience. Tracking client-side requests and their response times is key to fully understanding network performance.

  • Target: 1 second

Screen loading

Optimizing screen transitions and content loading times helps ensure a smooth, uninterrupted user experience. Instabug’s App Performance Monitoring detects delays in content loading stages. Loading times can vary depending on the type and amount of content—for longer wait times, use progress indicators to manage user expectations.

Execution traces

Every app is built differently; you’ll need to assess custom client-side logic and see how long it takes to execute specific traces in your app. Tracking individual traces in addition to overall performance will help you identify and resolve issues faster, quickly stacking targeted improvements.

  • Target: 2 seconds

Five Performance Metrics, One Way to Measure Them

Apdex (Application Performance Index) is an industry-standard metric used to track and measure user satisfaction based on performance; a combination of speed and stability, factoring in multiple performance inputs. Scores range from 0 to 1, with 1 being perfect. Apdex simplifies quantifying performance and allows your team to align around a standardized quality metric that can be used to set targets, create performance alerts, and monitor changes over time.

Your Apdex score factors in all of the performance issues and metrics that impact the user experience, including crashes, UI hangs or freezes, app launches, and network calls.

Apdex scores can be more useful than traditional KPIs like wait times because they represent a holistic view of app performance and can be calibrated to specific use cases. If you’re using Instabug, for example, you can add and subtract key metrics, variables you want to contribute to your overall Apdex score. This allows you to set performance thresholds that are specific to your app, rather than aiming for general benchmarks. You can use Apdex for overall app performance as well as individual metrics and transactions.

Apdex scores range from 0 to 1, with 1 being perfect performance. With Instabug APM, you can set alerts for when your overall Apdex or metric-specific scores drop.

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