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Expo Observe

A library that collects app performance metrics and dispatches them to EAS Observe.

Android
iOS
tvOS
Recommended version:
~0.2.4

expo-observe is a library that collects performance metrics from your app and dispatches them to EAS Observe, a performance monitoring service from Expo, or to your preferred OpenTelemetry (OTEL)-compliant backend. It measures real-world startup performance, such as Time to First Render (TTR) and Time to Interactive (TTI), from apps running in production.

Installation

Terminal
npx expo install expo-observe

If you are installing this in an existing React Native app, make sure to install expo in your project.

Configuration

In release builds, installing the expo-observe library is all that is needed to configure the library to start sending startup metrics (though you will need to follow the usage instructions below to call AppMetrics.markInteractive to track TTI). The library will not dispatch events in debug builds, but you can change this and other config options such as sample rate and environment name with the AppMetrics.configure({}) call. For all available options, see the EAS Observe configuration guide.

Usage

On SDK 55, wrap your root layout with AppMetricsRoot to measure Time to First Render automatically. Then, call AppMetrics.markInteractive when your app is ready for user interaction to record Time to Interactive:

src/app/_layout.tsx
import { AppMetrics, AppMetricsRoot } from 'expo-observe'; import { Stack } from 'expo-router'; import { useEffect } from 'react'; function RootLayout() { useEffect(() => { // Call markInteractive() after any initialization work behind the // splash screen completes. AppMetrics.markInteractive(); }, []); return <Stack />; } export default AppMetricsRoot.wrap(RootLayout);

For step-by-step instructions, including how to handle apps with multiple entry screens, see the EAS Observe Get started guide.

API

import { AppMetrics, AppMetricsRoot } from 'expo-observe';

Component

AppMetricsRoot

Android
iOS
tvOS

Type: React.Element<{ children: ReactNode }>

A root component that automatically marks the first render. Wrap your app's root component with this to measure time to first render without manually calling AppMetrics.markFirstRender().

Interfaces

ExpoObserveModuleType

Android
iOS
tvOS

ExpoObserveModuleType Methods

configure(config)

Android
iOS
tvOS
ParameterTypeDescription
configConfig

Observability settings to apply.


Configures how observability events are collected and dispatched at runtime, such as the environment label, dispatching behavior, and sampling.

Returns:
void

Example

import Observe from 'expo-observe'; Observe.configure({ environment: 'production', dispatchingEnabled: true, });

dispatchEvents()

Android
iOS
tvOS

Dispatches pending events to the server immediately.

Events are dispatched automatically when the app moves to the background. On Android, a background worker dispatches events once network connectivity is available. On iOS, dispatching happens when the app resigns active state or is about to terminate. Call this method to flush events manually, for example, during testing or to ensure events are sent before a specific point.

Returns:
Promise<void>

A promise that resolves when the pending events have been dispatched.

Example

import Observe from 'expo-observe'; await Observe.dispatchEvents();

Metric

Android
iOS
tvOS
PropertyTypeDescription
categorystring
-
namestring
-
params(optional)Record<string, unknown>
-
routeName(optional)string
-
sessionIdstring
-
timestampstring
-
valuenumber
-

Types

Config

Android
iOS
tvOS
PropertyTypeDescription
dispatchInDebug(optional)boolean

Whether to dispatch metrics that were collected in a debug build of the host app.

When false, metrics produced by debug builds are marked as sent without being dispatched. When true, debug-build metrics are dispatched alongside release-build metrics.

Has no effect on release builds.

If dispatchingEnabled is false or this device is out-of-sample for sampleRate, nothing is dispatched regardless of dispatchInDebug.

Default:false
dispatchingEnabled(optional)boolean

Whether to dispatch observability events to the server.

When false, any pending metrics are marked as sent without being dispatched and no further metrics are dispatched until this is set back to true.

Default:true
environment(optional)string

The environment for observability events

Default:process.env.NODE_ENV
sampleRate(optional)number

Fraction of installations that should dispatch metrics, in [0, 1]. Values outside that range are clamped.

The decision is deterministic per installation — a device is either permanently in-sample or out-of-sample for a given rate, so the choice is stable across app launches.

Interaction with dispatchingEnabled:

  • If dispatchingEnabled is false, metrics are never dispatched
  • If dispatchingEnabled is true (or unset), metrics are dispatched only when this device is in-sample.
Default:undefined - metrics from all devices are sent

MetricAttributes

Android
iOS
tvOS
PropertyTypeDescription
params(optional)Record<string, unknown>

Custom parameters to attach to the metric.

routeName(optional)string

Name of the route associated with the metric. Some metrics populate this with a sensible default when omitted — for example, the TTI metric falls back to the initial route name detected from the router.