Join us for Firebase Summit on November 10, 2021. Tune in to learn how Firebase can help you accelerate app development, release with confidence, and scale with ease. Register

Customize your Firebase Crashlytics crash reports

This guide describes how to customize your crash reports using the Firebase Crashlytics SDK. By default, Crashlytics automatically collects crash reports for all your app's users (you can turn off automatic crash reporting and enable opt-in reporting for your users instead). Crashlytics provides four logging mechanisms out of the box: custom keys, custom logs, user identifiers, and caught exceptions.

Add custom keys

Custom keys help you get the specific state of your app leading up to a crash. You can associate arbitrary key/value pairs with your crash reports, then use the custom keys to search and filter crash reports in the Firebase console.

  • In the Crashlytics dashboard, you can search for issues that match a custom key.

  • When you're reviewing a specific issue in the console, you can view the associated custom keys for each event (Keys subtab) and even filter the events by custom keys (Filter menu at the top of the page).

Use the setCustomKey instance method to set key/value pairs. Note that setCustomKey is overloaded for the value parameter to accept any primitive or String argument. Here are some examples:


FirebaseCrashlytics crashlytics = FirebaseCrashlytics.getInstance();

crashlytics.setCustomKey("my_string_key", "foo" /* string value */);

crashlytics.setCustomKey("my_bool_key", true /* boolean value */);

crashlytics.setCustomKey("my_double_key", 1.0 /* double value */);

crashlytics.setCustomKey("my_float_key", 1.0f /* float value */);

crashlytics.setCustomKey("my_int_key", 1 /* int value */);


val crashlytics = Firebase.crashlytics
crashlytics.setCustomKeys {
    key("my_string_key", "foo") // String value
    key("my_bool_key", true)    // boolean value
    key("my_double_key", 1.0)   // double value
    key("my_float_key", 1.0f)   // float value
    key("my_int_key", 1)        // int value

You can also modify the value of an existing key by calling the key and setting it to a different value. For example:


FirebaseCrashlytics crashlytics = FirebaseCrashlytics.getInstance();

crashlytics.setCustomKey("current_level", 3);
crashlytics.setCustomKey("last_UI_action", "logged_in");


val crashlytics = Firebase.crashlytics
crashlytics.setCustomKeys {
    key("current_level", 3)
    key("last_UI_action", "logged_in")

Add key/value pairs in bulk by passing an instance of CustomKeysAndValues to the setCustomKeys instance method:


CustomKeysAndValues keysAndValues = new CustomKeysAndValues.Builder()
.putString("string key", "string value")
.putString("string key 2", "string  value 2")
.putBoolean("boolean key", True)
.putBoolean("boolean key 2", False)
.putFloat("float key", 1.01)
.putFloat("float key 2", 2.02)



For Kotlin, the existing functionality is simpler than using the CustomKeysAndValues builder.

crashlytics.setCustomKeys {
  key("str_key", "hello")
  key("bool_key", true)
  key("int_key", 1)
  key("long_key", 1L)
  key("float_key", 1.0f)
  key("double_key", 1.0)

Add custom log messages

To give yourself more context for the events leading up to a crash, you can add custom Crashlytics logs to your app. Crashlytics associates the logs with your crash data and displays them in the Crashlytics page of the Firebase console, under the Logs tab.

Use log to help pinpoint issues. For example:





Set user identifiers

To diagnose an issue, it’s often helpful to know which of your users experienced a given crash. Crashlytics includes a way to anonymously identify users in your crash reports.

To add user IDs to your reports, assign each user a unique identifier in the form of an ID number, token, or hashed value:





If you ever need to clear a user identifier after you set it, reset the value to a blank string. Clearing a user identifier does not remove existing Crashlytics records. If you need to delete records associated with a user ID, contact Firebase support.

(Android NDK only) Add metadata to NDK crash reports

You can optionally include the crashlytics.h header in your C++ code to add metadata to NDK crash reports, such as custom keys, custom logs, user identifiers. All these options are described on this page above.

crashlytics.h is available as a header-only C++ library in the Firebase Android SDK GitHub Repository.

Read the comments in the header file for instructions on using the NDK C++ APIs.

Report non-fatal exceptions

In addition to automatically reporting your app’s crashes, Crashlytics lets you record non-fatal exceptions and sends them to you the next time your app launches.

Use the recordException method to record non-fatal exceptions in your app's catch blocks. For example:


try {
} catch (Exception e) {
    // handle your exception here


try {
} catch (e: Exception) {
    // handle your exception here

All recorded exceptions appear as non-fatal issues in the Firebase console. The issue summary contains all the state information you normally get from crashes, along with breakdowns by Android version and hardware device.

Crashlytics processes exceptions on a dedicated background thread to minimize the performance impact to your app. To reduce your users’ network traffic, Crashlytics batches logged exceptions together and sends them the next time the app launches.

Enable opt-in reporting

By default, Crashlytics automatically collects 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 reporting and only sending data to Crashlytics when you choose to in your code:

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

        android:value="false" />
  2. Enable collection for select users by calling the Crashlytics data collection override at runtime. The override value persists across launches of your app so Crashlytics can automatically collect reports. 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.





Manage Crash Insights data

Crash Insights helps you resolve issues by comparing your anonymized stack traces to traces from other Firebase apps and letting you know if your issue is part of a larger trend. For many issues, Crash Insights even provides resources to help you debug the crash.

Crash Insights uses aggregated crash data to identify common stability trends. If you’d prefer not to share your app's data, you can opt-out of Crash Insights from the Crash Insights menu at the top of your Crashlytics issue list in the Firebase console.