Customize your Firebase Crashlytics crash reports

In the Crashlytics dashboard, you can click into an issue and get a detailed event report. You can customize those reports to help you better understand what's happening in your app and the circumstances around events reported to Crashlytics.

  • Automatically get breadcrumb logs if your app uses the Firebase SDK for Google Analytics. These logs give you visibility into user actions leading up to a Crashlytics-collected event in your app.

  • Turn off automatic crash reporting and enable opt-in reporting for your users. Note that, by default, Crashlytics automatically collects crash reports for all your app's users.

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 setCustomValue method to set key/value pairs. For example:


// Set int_key to 100.
Crashlytics.crashlytics().setCustomValue(100, forKey: "int_key")

// Set str_key to "hello".
Crashlytics.crashlytics().setCustomValue("hello", forKey: "str_key")


When setting integers, booleans, or floats, box the value as @(value).

// Set int_key to 100.
[[FIRCrashlytics crashlytics] setCustomValue:@(100) forKey:@"int_key"];

// Set str_key to "hello".
[[FIRCrashlytics crashlytics] setCustomValue:@"hello" forKey:@"str_key"];

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


Crashlytics.crashlytics().setCustomValue(100, forKey: "int_key")

// Set int_key to 50 from 100.
Crashlytics.crashlytics().setCustomValue(50, forKey: "int_key")


[[FIRCrashlytics crashlytics] setCustomValue:@(100) forKey:@"int_key"];

// Set int_key to 50 from 100.
[[FIRCrashlytics crashlytics] setCustomValue:@(50) forKey:@"int_key"];

Add key/value pairs in bulk by using the setCustomKeysAndValues method with an NSDictionary as the only parameter:


let keysAndValues = [
                 "string key" : "string value",
                 "string key 2" : "string value 2",
                 "boolean key" : true,
                 "boolean key 2" : false,
                 "float key" : 1.01,
                 "float key 2" : 2.02
                ] as [String : Any]



NSDictionary *keysAndValues =
    @{@"string key" : @"string value",
      @"string key 2" : @"string value 2",
      @"boolean key" : @(YES),
      @"boolean key 2" : @(NO),
      @"float key" : @(1.01),
      @"float key 2" : @(2.02)};

[[FIRCrashlytics crashlytics] setCustomKeysAndValues: keysAndValues];

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() or log(format:, arguments:) to help pinpoint issues. If you want to get a useful log output with messages, the object that you pass to log() must conform to the CustomStringConvertible property. log() returns the description property you define for the object. For example:

Crashlytics.crashlytics().log("Higgs-Boson detected! Bailing out…, \(attributesDict)")

.log(format:, arguments:) formats values returned from calling getVaList(). For example:

Crashlytics.crashlytics().log(format: "%@, %@", arguments: getVaList(["Higgs-Boson detected! Bailing out…", attributesDict]))

For more details on how to use log() or log(format:, arguments:), refer to the Crashlytics reference documentation.


Use log or logWithFormat to help pinpoint issues. Note that if you want to get a useful log output with messages, the object that you pass to either method must override the description instance property. For example:

[[FIRCrashlytics crashlytics] log:@"Simple string message"];

[[FIRCrashlytics crashlytics] logWithFormat:@"Higgs-Boson detected! Bailing out... %@", attributesDict];

[[FIRCrashlytics crashlytics] logWithFormat:@"Logging a variable argument list %@" arguments:va_list_arg];

For more details on how to use log and logWithFormat, refer to the Crashlytics reference documentation.

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:




[[FIRCrashlytics crashlytics] setUserID:@"123456789"];

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.

Get breadcrumb logs

Breadcrumb logs give you a better understanding of the interactions that a user had with your app leading up to a crash, non-fatal, or ANR event. These logs can be helpful when trying to reproduce and debug an issue.

Breadcrumb logs are powered by Google Analytics, so to get breadcrumb logs, you need to enable Google Analytics for your Firebase project and add the Firebase SDK for Google Analytics to your app. Once these requirements are met, breadcrumb logs are automatically included with an event's data within the Logs tab when you view the details of an issue.

The Analytics SDK automatically logs the screen_view event which enables the breadcrumb logs to show a list of screens viewed before the crash, non-fatal, or ANR event. A screen_view breadcrumb log contains a firebase_screen_class parameter.

Breadcrumb logs are also populated with any custom events that you manually log within the user’s session, including the event's parameter data. This data can help show a series of user actions leading up to a crash, non-fatal, or ANR event.

Note that you can control the collection and use of Google Analytics data, which includes the data that populates breadcrumb logs.

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. Turn off automatic collection by adding a new key to your Info.plist file:

    • Key: FirebaseCrashlyticsCollectionEnabled
    • 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.




    [[FIRCrashlytics crashlytics] setCrashlyticsCollectionEnabled:YES];

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.