Using Firebase Crashlytics

To start using Firebase Crashlytics within your project, import it at the top of your project files:

import 'package:firebase_crashlytics/firebase_crashlytics.dart';

Sending reports to Crashlytics

To send report data to Crashlytics, the application must be restarted. Crashlytics automatically sends any crash reports to Firebase the next time the application is launched.

Toggle Crashlytics collection

Call the setCrashlyticsCollectionEnabled method to toggle Crashlytics collection status.

For example to ensure it is disabled when your app is in debug mode you can do the following:

import 'package:flutter/foundation.dart' show kDebugMode;
// ...
if (kDebugMode) {
// Force disable Crashlytics collection while doing every day development.
// Temporarily toggle this to true if you want to test crash reporting in your app.
await FirebaseCrashlytics.instance
} else {
// Handle Crashlytics enabled status when not in Debug,
// e.g. allow your users to opt-in to crash reporting.

You can additionally read the current collection enabled status:

if (FirebaseCrashlytics.instance.isCrashlyticsCollectionEnabled) {
// Collection is enabled.

Forcing a crash

You don't have to wait for a crash to know that Crashlytics is working. To force a crash, call the crash method:


Your app should exit immediately after calling this method. After opening your app again after the crash Firebase Crashlytics will upload the crash report to the Firebase Console.

The error will be show on the Firebase Crashlytics dashboard as an instance of FirebaseCrashlyticsTestCrash, with a message of This is a test crash caused by calling .crash() in Dart.

Add custom keys

To associate key/value pairs with your crash reports, you can use the setCustomKey method

// Set a key to a string.
FirebaseCrashlytics.instance.setCustomKey('str_key', 'hello');
// Set a key to a boolean.
FirebaseCrashlytics.instance.setCustomKey("bool_key", true);
// Set a key to an int.
FirebaseCrashlytics.instance.setCustomKey("int_key", 1);
// Set a key to a long.
FirebaseCrashlytics.instance.setCustomKey("int_key", 1L);
// Set a key to a float.
FirebaseCrashlytics.instance.setCustomKey("float_key", 1.0f);
// Set a key to a double.
FirebaseCrashlytics.instance.setCustomKey("double_key", 1.0);

This accepts a maximum of 64 key/value pairs. New keys beyond that limit are ignored. Keys or values that exceed 1024 characters are truncated.

Add custom log messages

To add custom Crashlytics log messages to your app, use the log method

FirebaseCrashlytics.instance.log("Higgs-Boson detected! Bailing out");

Set user identifiers

To add user IDs to your reports, assign each user with a unique ID. This can be an ID number, token or hashed value:


Handling uncaught errors

By overriding FlutterError.onError with FirebaseCrashlytics.instance.recordFlutterError, it will automatically catch all errors that are thrown within the Flutter framework.

void main() {
// Pass all uncaught errors from the framework to Crashlytics.
FlutterError.onError = FirebaseCrashlytics.instance.recordFlutterError;

Zoned Errors

If you want to catch errors that occur in zones, you can pass FirebaseCrashlytics.instance.recordError to the second parameter of runZonedGuarded

runZonedGuarded<Future<void>>(() async {
// ...
}, FirebaseCrashlytics.instance.recordError);

Errors outside of Flutter

To catch errors that happen outside of the Flutter context, install an error listener on the current Isolate:

Isolate.current.addErrorListener(RawReceivePort((pair) async {
final List<dynamic> errorAndStacktrace = pair;
await FirebaseCrashlytics.instance.recordError(

Enable opt-in reporting

By default, Crashlytics will automatically collect crash reports for all your app's users. To give users more control over the data they send, you can enable opt-in reporting by disabling automatic collection and initializing Crashlytics only for selected users:

  1. Turn off automatic collection natively:

a. Android In the application block of your AndroidManifest.xml file, add a meta-data tags to turn off automatic collection:

android:value="false" />

b. iOS

Add a new key to your Info.plist file.

  • Key: FirebaseCrashlyticsCollectionEnabled
  • Value: false
  1. Enable collection for select users by calling the Crashlytics data collection override at runtime. To opt out of automatic crash reporting, pass false as the override value. When set to false, the new value does not apply until the next run of the app.