open class AppException : RealmException

Top level class for all exceptions that are specific to using App Services and Device Sync.

Subclasses of this class fall into two broad categories: ServiceException and SyncException.

  1. ServiceException's are thrown by all API's that talk directly to App Services through HTTP requests. The io.realm.mongodb.App, io.realm.mongodb.User and [io.realm.mongodb.EmailPasswordAuth classes handle HTTP requests for the SDK.

  2. SyncException's are thrown by errors caused when using Device Sync APIs, i.e realms opened using a io.realm.mongodb.SyncConfiguration. These errors propagate through the io.realm.mongodb.SyncConfiguration.Builder.errorHandler.

Each of these categories are divided further:

Exceptions at the bottom of the hierarchy are actionable, i.e. it should be clear from the exception which action can be taken to resolve it.

Exceptions further up the hierarchy categorize the errors. They can be harder to react to in a single way that will make sense to end users of an app, but should be logged for later inspection.

In most cases, only exceptions at the bottom of the hierarchy will be documented in the API documentation, with one notable special case: ConnectionException. This exception is assumed to be thrown by all methods that mentions a ServiceException and covers all transport errors. These are often intermittent, so catching this exception and retrying should generally be safe, but more information can be found in the documentation for ConnectionException.

With the above exception hierarchy in mind, a sensible way to handle errors could look like this:

val app = App.with("my-app-id")
runCatching {
app.login(Credentials.emailPassword("", "mypassword"))
}.onSuccess {
}.onFailure { ex: Throwable ->
when(ex) {
is InvalidCredentialsException -> {
is ConnectionException -> {
else -> {

For more information about specific exceptions, see the documentation for that exception.

See also


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open val cause: Throwable?
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open val message: String?


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