Customizing error reports

In order to quickly reproduce and fix errors, it is often helpful to send additional application-specific diagnostic “metadata” to your BugSnag dashboard to provide a rich context that is also available for searching and filtering.

You can also amend the events captured by BugSnag to adjust the information shown on the dashboard and even choose not to send the event at all.

Updating events using callbacks

If you’d like to add diagnostic data to reports, or adjust event data conditionally, you can register a block to be run before an error is delivered to your BugSnag dashboard:

BugsnagConfiguration *config = [BugsnagConfiguration loadConfig];
[config addOnSendErrorBlock:^BOOL (BugsnagEvent *event) {
    [event addMetadata:@"Acme Co." withKey:@"name" toSection:@"account"];
    [event addMetadata:@(YES) withKey:@"paying_customer" toSection:@"account"];

    // Return `NO` if you'd like to stop this error being reported
    return YES;
[Bugsnag startWithConfiguration:config];
let config = BugsnagConfiguration.loadConfig()
config.addOnSendError { (event) -> Bool in
    event.addMetadata("Acme Co.", key:"name", section:"account")
    event.addMetadata(true, key:"paying_customer", section:"account")

    // Return `false` if you'd like to stop this error being reported
    return true
Bugsnag.start(with: config)

The callback gives you access to an event object, so you can inspect and modify the error event which is about to be sent to BugSnag.

If the app has crashed, these delivery-time callbacks will be executed when the app next launches and has network connectivity. They are invoked on a dedicated background queue, which will be different from the queue where the block was originally added. This means the state of the app and device are likely to be different to how they were when the crash occurred and so care must be taken when reading or adding external data in a callback. See Crash-time handler for information on capturing data during a crash.

Discarding events

If you want to prevent an event from being sent to BugSnag, you can return false within the callback block. This would allow for users to opt out of sending error reports, for example:

BugsnagConfiguration *config = [BugsnagConfiguration loadConfig];
[config addOnSendErrorBlock:^BOOL (BugsnagEvent *event) {
    return ![self userHasOptedOut];
[Bugsnag startWithConfiguration:config];
let config = BugsnagConfiguration.loadConfig()
config.addOnSendError { (event) -> Bool in
    return !self.userHasOptedOut()
Bugsnag.start(with: config)

Crash-time handler

When a crash occurs in an application, information about the runtime state of the application is collected and written to a crash file to be sent to BugSnag at the next opportunity. The onCrashHandler hook allows you to execute additional code during the crash, before the data is written to file.

However because the callback is executing at crash-time, it must be asynchronous-safe. This greatly reduces the functionality that can safely be executed: in particular this means that Objective-C code cannot be used. A C function can be registered as follows:

// Create crash handler
#import <Bugsnag/BSG_KSCrashReportWriter.h>

void HandleCrashedThread(const BSG_KSCrashReportWriter *writer) {
  // add metadata
  writer->beginObject(writer, "account");
  writer->addStringElement(writer, "name", "Acme Co.");
  // possibly serialize data, call another crash reporter, ...
// Assign crash handler function to the configuration
BugsnagConfiguration *config = [BugsnagConfiguration loadConfig];
config.onCrashHandler = &HandleCrashedThread;
[Bugsnag startWithConfiguration:config];
// Assign crash handler function to the configuration
let config = BugsnagConfiguration.loadConfig()
config.onCrashHandler = HandleCrashedThread
Bugsnag.start(with: config)

The writer parameter provided allows you to add data to the crash report file (in JSON format), which will later be sent to your dashboard where your data will appear as metadata in the reported event. The data added to writer must be a string at the top-level with a dictionary value, which can have an arbitrary structure inside it. In this way, the top-level string will be the section (or tab) in which the data appears in your dashboard. See BSG_KSCrashReportWriter.h for a list of available operations.

The data is available in the event passed to delivery-time callbacks where it can be queried or amended in a more hospitable environment:

BugsnagConfiguration *config = [BugsnagConfiguration loadConfig];
[config addOnSendErrorBlock:^BOOL (BugsnagEvent *event) {
    NSDictionary *accountData = [event getMetadataFromSection:@"account"];
    // Perform actions based on crash-time data
    return YES;
[Bugsnag startWithConfiguration:config];
let config = BugsnagConfiguration.loadConfig()
config.addOnSendError { (event) -> Bool in
    let accountData = event.getMetadata(section: "account")
    // Perform actions based on crash-time data
    return true
Bugsnag.start(with: config)

Global metadata

If you have metadata that is applicable to all captured events, it can be set globally on the BugSnag client and will be set on all subsequently generated events. To ensure that events contain metadata as soon as BugSnag starts capturing events, use the addMetadata functions on the Configuration class.

Data is added to a specified “section”, which is displayed as a tab in the BugSnag dashboard, and can either be added individually or as a dictionary:

BugsnagConfiguration *config = [BugsnagConfiguration loadConfig];
[config addMetadata:@"Acme Co." withKey:@"name" toSection:@"account"];
[config addMetadata:@{ @"delivery": @"express", @"sale": @"spring" }
[Bugsnag startWithConfiguration:config];
let config = BugsnagConfiguration.loadConfig()
config.addMetadata("Acme Co.", key: "name", section: "account")
config.addMetadata(["delivery": "express", "sale": "spring"],
                   section: "basket")
Bugsnag.start(with: config)

Metadata can also be managed whilst your application is running using addMetadata and clearMetadata on the Bugsnag client:

[Bugsnag addMetadata:@"Acme Co." withKey:@"name" toSection:@"account"];
// ...
[Bugsnag clearMetadataFromSection:@"account"];
Bugsnag.addMetadata("Acme Co.", key: "name", section: "account")
// ...
Bugsnag.clearMetadata(section: "account")

Adding user data

Information about the user affected by errors can be added to events sent to your BugSnag dashboard by setting an initial user ID, email and name in Configuration when BugSnag starts:

BugsnagConfiguration *config = [BugsnagConfiguration loadConfig];
[config setUser:@"3" withEmail:@"" andName:@"Bugs Nag"];
[Bugsnag startWithConfiguration:config];
let config = BugsnagConfiguration.loadConfig()
config.setUser("3", withEmail: "", andName: "Bugs Nag")
Bugsnag.start(with: config)

When the persistUser configuration option is set to true, this user information will also be set in subsequent application launches.

If the user changes whilst the application is running, for example if a user signs in, you can update the user data on the BugSnag client for all subsequent events:

[Bugsnag setUser:@"3" withEmail:@"" andName:@"Bugs Nag"];
Bugsnag.setUser("3", withEmail: "", andName: "Bugs Nag")

You can use metadata to add additional user information to the “user” section.

Setting context

BugSnag uses the concept of “contexts” to help display and group your errors. The context represents what was happening in your application at the time an error occurs and is given high visual prominence in the dashboard.

By default this is set to the file name and line number of the topmost in-project stackframe. If you would like to set this value manually, you can set it with an initial value in Configuration when BugSnag starts:

BugsnagConfiguration *config = [BugsnagConfiguration loadConfig];
config.context = @"InitialTutorialStep";
[Bugsnag startWithConfiguration:config];
let config = BugsnagConfiguration.loadConfig()
config.context = "InitialTutorialStep"
Bugsnag.start(with: config)

The context can then be amended on the Bugsnag client as/when it changes for all subsequent events:

[Bugsnag setContext:@"SecondTutorialStep"];

Alternatively, the context can be amended for each event using a callback block:

BugsnagConfiguration *config = [BugsnagConfiguration loadConfig];
[config addOnSendErrorBlock:^BOOL (BugsnagEvent *event) {
    event.context = @"SecondTutorialStep";
    return YES;
[Bugsnag startWithConfiguration:config];
let config = BugsnagConfiguration.loadConfig()
config.addOnSendError { (event) -> Bool in
    event.context = "SecondTutorialStep"
    return true
Bugsnag.start(with: config)

The BugsnagEvent class

A BugsnagEvent object represents an error captured by BugSnag and is available as a parameter on an event callback block. The following properties and methods are available on an Event for you to query and update the captured data.


Declare a single feature flag or experiment with variant as an optional second parameter.

[event addFeatureFlagWithName:@"Checkout button color" variant:@"Blue"];
[event addFeatureFlagWithName:@"New checkout flow"];
event.addFeatureFlag(name: "Checkout button color", variant: "Blue")
event.addFeatureFlag(name: "New checkout flow")


Declare multiple feature flags or experiments.

[event addFeatureFlags:@[
    [BugsnagFeatureFlag flagWithName:@"Checkout button color" variant:@"Blue"],
    [BugsnagFeatureFlag flagWithName:@"Special offer" variant:@"Free Coffee"],
    [BugsnagFeatureFlag flagWithName:@"New checkout flow"]]];
    BugsnagFeatureFlag(name: "Checkout button color", variant: "Blue"),
    BugsnagFeatureFlag(name: "Special offer", variant: "Free Coffee"),
    BugsnagFeatureFlag(name: "New checkout flow")])


Adds the specified key and value in the specified section, which is shown as a tab on the BugSnag dashboard.

Data can be added key-by-key with a value that is a primitive type or a collection such as a dictionary or array:

[event addMetadata:@"Acme Co." withKey:@"name" toSection:@"account"];
[event addMetadata:@(YES) withKey:@"paying_customer" toSection:@"account"];
[event addMetadata:@[@"basic", @"admin"] withKey:@"roles" toSection:@"account"];
event.addMetadata("Acme Co.", key: "name", section: "account")
event.addMetadata(true, key: "name", section: "account")
event.addMetadata(["basic", "admin"], key: "roles", section: "account")

Alternatively a whole dictionary can be added for a section:

[event addMetadata:@{ @"delivery": @"express", @"sale": @"spring" }
event.addMetadata(["delivery": "express", "sale": "spring"],
                  section: "basket")

Metadata set on the event will be combined with global metadata set on the Bugsnag client, with properties on the Event taking precedence.


The API key used for events sent to BugSnag. Even though the API key is set when BugSnag is initialized, you may choose to send certain events to a different BugSnag project:

NSString *apiKey = event.apiKey;
var apiKey = event.apiKey


Information about your app can be found in the app object:

property type description
binaryArch String The architecture of the running application binary
bundleVersion String The bundle version used by the application
codeBundleId String The revision ID from the manifest (React Native apps only)
dsymUuid String Unique identifier for the debug symbols file corresponding to the application
duration Number The number of milliseconds the application was running before the event occurred
durationInForeground Number The number of milliseconds the application was running in the foreground before the event occurred
id String The package name of the application
inForeground Boolean Whether the application was in the foreground when the event occurred
isLaunching Boolean Whether the application was still launching when the event occurred
releaseStage String The release stage set in Configuration
type String The application type set in Configuration
version String The version of the application set in Configuration

These values can be accessed and amended if necessary: = [self getCustomBundleVersion]; = getCustomBundleVersion()

A list of breadcrumbs leading up to the event can be found in event.breadcrumbs. See the Breadcrumb class for details of the data available.

These values can be accessed and amended if necessary:

event.breadcrumbs[0].message = @"Left home screen";
event.breadcrumbs?[0].message = "Left home screen"


Remove a single feature flag or experiment.

[event clearFeatureFlagWithName:@"Checkout button color"];
event.clearFeatureFlag(name: "Checkout button color")


Remove all feature flags and experiments.

[event clearFeatureFlags];


Removes all the data from the specified section or from a key in the section:

[event clearMetadataFromSection:@"account"];
// or
[event clearMetadataFromSection:@"account" withKey:@"name"];
event.clearMetadata(section: "account")
// or
event.clearMetadata(section: "account", key: "name")


The context represents what was happening in your application at the time an error occurs.

event.context = @"SecondTutorialStep";
event.context = "SecondTutorialStep"

See Setting context for more information.


Information about the device on which the event occurred can be found in event.device:

property type description
freeMemory Number The number of free bytes of memory available on the device
id String A UUID generated by BugSnag and used for the individual application on a device
jailbroken String Whether the device has been jailbroken
locale String The IETF language tag of the locale used
manufacturer String The manufacturer of the device used
model String The model name of the device used
orientation String The orientation of the device when the event occurred: either portrait or landscape
osName String The name of the operating system running on the device used
osVersion String The version of the operating system running on the device used
runtimeVersions Map A collection of names and their versions of the primary languages, frameworks or runtimes that the application is running on
time String The timestamp on the device when the event occurred
totalMemory Number The total number of bytes of memory on the device

These values can be accessed and amended if necessary:

event.device.locale = @"de-DE";
event.device.locale = "de-DE"

device.freeDisk is now only populated on macOS due to Apple’s restrictions on APIs that could be used for fingerprinting on iOS, tvOS and watchOS.


event.errors is an array of one or more Error objects. The first item in the list represents the signal or thrown object. Each subsequent item represents the exception that caused the preceding one.

A reference to the actual error object that caused the event (if applicable) is available through event.originalError.

An Error object contains the following information:

property type description
errorClass String The class of the error generating the event
errorMessage String The message of or reason for the error generating the event
stacktrace List<Stackframe> A representation of the stacktrace
type Error.Type The type of error based on the originating platform
event.errors[0].errorClass = @"MyErrorClass";
event.errors[0].errorClass = "MyErrorClass"

In an Error object, the stacktrace is a list of the following Stackframe objects:

property type description
frameAddress String The stack frame address
isLr String Whether the frame was within the link register
isPc String Whether the frame was within the program counter
machoFile String The Mach-O file used by the stackframe
machoLoadAddress String The load address of the Mach-O file
machoUuid String A UUID identifying the Mach-O file used by the stackframe
machoVmAddress String The VM address of the Mach-O file
method String The name of the method that was being executed
symbolAddress String The address of the stackframe symbol

#Modifying stack traces

If you use a wrapper function to send handled events, you can trim the function from the event’s stack trace:

NSMutableArray<BugsnagStackframe *> *frames = event.errors[0].stacktrace.mutableCopy;
[frames removeObjectAtIndex:0];
event.errors[0].stacktrace = frames;
event.errors[0].stacktrace.remove(at: 0)


Returns a list of feature flags active at the time of the event.

NSArray<BugsnagFeatureFlag *> *features = event.featureFlags
var features =  = event.featureFlags

For more information, see Feature flags & experiments.


Returns a map of data in the specified section and optionally key:

NSDictionary *metadata = [event getMetadataFromSection:@"account"];
// or
NSString *accountName = [event getMetadataFromSection:@"account" withKey:@"name"];
var metadata = event.getMetadata(section: "account")
// or
var accountName = event.getMetadata(section: "account", key: "name")


The grouping hash of the event to override the default grouping on the dashboard. All events with the same grouping hash will be grouped together into one error. This is an advanced usage of the library and mis-using it will cause your events not to group properly in your dashboard.

As the name implies, this option accepts a hash of sorts.

// ... generate the hash
NSString *groupingHash = @"f8803769f3e293dfcabdb6dec5100b8c52c6ae6b";
event.groupingHash = groupingHash;
// ... generate the hash
var groupingHash = "f8803769f3e293dfcabdb6dec5100b8c52c6ae6b"
event.groupingHash = groupingHash


The original object that caused the error in your application. This value will only be populated for non-fatal errors which did not terminate the process, and will contain an NSError or NSException.

Manipulating event.originalError does not affect the error information reported to the BugSnag dashboard. Use event.errors to access and amend the representation of the error that will be sent.

if ((event.originalError != nil) &&
    [event.originalError isKindOfClass:NSError.class]) {
    if([((NSError *)event.originalError).domain isEqualToString:@"myDomain"]) {
        // ...
if let error = event.originalError as? NSError {
    if error.domain == "myDomain" {
        // ...


Sets the current user information.

[event setUser:@"3" withEmail:@"" andName:@"Bugs Nag"];
event.setUser("3", withEmail: "", andName: "Bugs Nag")

nil can be used as a parameter value to clear the user attribute.


The severity of the event. By default, unhandled exceptions will be Severity.ERROR and handled exceptions sent with Bugsnag.notify will be Severity.WARNING.

event.severity = BSGSeverityWarning;
event.severity = .warning


If thread state is being captured along with the event, event.threads will contain a list of Thread objects as follows:

property type description
id Number A unique ID which identifies this thread
errorReportingThread Boolean Whether the thread was the thread that caused the event
name String The name of the thread (from java.lang.Thread)
stacktrace List<Stackframe> A representation of the stacktrace when the event occurred
state Thread.State The state of the thread when the event occurred
type Thread.Type The type of thread based on the originating platform
event.threads[0].name = @"New name";
event.threads[0].name = "New name"


By default this is true if the event was automatically detected by BugSnag and false if it was reported manually via Bugsnag.notify. See our product pages for more information on handled vs unhandled events.

event.unhandled = YES;
event.unhandled = true

Changing the unhandled flag for an event will affect how it contributes to your application’s stability score.


Returns the current user information.

NSString *userId =;
NSString *userEmail =;
NSString *userName =;
var userId =
var userEmail =
var userName =