Enable logging in the Speech SDK

Logging to file is an optional feature for the Speech SDK. During development logging provides additional information and diagnostics from the Speech SDK's core components. It can be enabled by setting the property Speech_LogFilename on a speech configuration object to the location and name of the log file. Logging is handled by a static class in Speech SDK’s native library. You can turn on logging for any Speech SDK recognizer or synthesizer instance. All instances in the same process write log entries to the same log file.


The log file name is specified on a configuration object. Taking the SpeechConfig as an example and assuming that you've created an instance called speechConfig:

speechConfig.SetProperty(PropertyId.Speech_LogFilename, "LogfilePathAndName");
speechConfig.setProperty(PropertyId.Speech_LogFilename, "LogfilePathAndName");
speechConfig->SetProperty(PropertyId::Speech_LogFilename, "LogfilePathAndName");
speech_config.set_property(speechsdk.PropertyId.Speech_LogFilename, "LogfilePathAndName")
[speechConfig setPropertyTo:@"LogfilePathAndName" byId:SPXSpeechLogFilename];
import ("github.com/Microsoft/cognitive-services-speech-sdk-go/common")

speechConfig.SetProperty(common.SpeechLogFilename, "LogfilePathAndName")

You can create a recognizer from the configuration object. This will enable logging for all recognizers.


If you create a SpeechSynthesizer from the configuration object, it will not enable logging. If logging is enabled though, you will also receive diagnostics from the SpeechSynthesizer.

JavaScript is an exception where the logging is enabled via SDK diagnostics as shown in the following code snippet:


Create a log file on different platforms

For Windows or Linux, the log file can be in any path the user has write permission for. Write permissions to file system locations in other operating systems may be limited or restricted by default.

Universal Windows Platform (UWP)

UWP applications need to be places log files in one of the application data locations (local, roaming, or temporary). A log file can be created in the local application folder:

StorageFolder storageFolder = ApplicationData.Current.LocalFolder;
StorageFile logFile = await storageFolder.CreateFileAsync("logfile.txt", CreationCollisionOption.ReplaceExisting);
speechConfig.SetProperty(PropertyId.Speech_LogFilename, logFile.Path);

Within a Unity UWP application, a log file can be created using the application persistent data path folder as follows:

    string logFile = Application.persistentDataPath + "/logFile.txt";
    speechConfig.SetProperty(PropertyId.Speech_LogFilename, logFile);

For more about file access permissions in UWP applications, see File access permissions.


You can save a log file to either internal storage, external storage, or the cache directory. Files created in the internal storage or the cache directory are private to the application. It is preferable to create a log file in external storage.

File dir = context.getExternalFilesDir(null);
File logFile = new File(dir, "logfile.txt");
speechConfig.setProperty(PropertyId.Speech_LogFilename, logFile.getAbsolutePath());

The code above will save a log file to the external storage in the root of an application-specific directory. A user can access the file with the file manager (usually in Android/data/ApplicationName/logfile.txt). The file will be deleted when the application is uninstalled.

You also need to request WRITE_EXTERNAL_STORAGE permission in the manifest file:

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="...">
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Within a Unity Android application, the log file can be created using the application persistent data path folder as follows:

string logFile = Application.persistentDataPath + "/logFile.txt";
speechConfig.SetProperty(PropertyId.Speech_LogFilename, logFile);

In addition, you need to also set write permission in your Unity Player settings for Android to "External (SDCard)". The log will be written to a directory you can get using a tool such as AndroidStudio Device File Explorer. The exact directory path may vary between Android devices, location is typically the sdcard/Android/data/your-app-packagename/files directory.

More about data and file storage for Android applications is available here.


Only directories inside the application sandbox are accessible. Files can be created in the documents, library, and temp directories. Files in the documents directory can be made available to a user.

If you are using Objective-C on iOS, use the following code snippet to create a log file in the application document directory:

NSString *filePath = [
  [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject]
[speechConfig setPropertyTo:filePath byId:SPXSpeechLogFilename];

To access a created file, add the below properties to the Info.plist property list of the application:


If you're using Swift on iOS, please use the following code snippet to enable logs:

let documentsDirectoryPathString = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first!
let documentsDirectoryPath = NSURL(string: documentsDirectoryPathString)!
let logFilePath = documentsDirectoryPath.appendingPathComponent("swift.log")
self.speechConfig!.setPropertyTo(logFilePath!.absoluteString, by: SPXPropertyId.speechLogFilename)

More about iOS File System is available here.

Logging with multiple recognizers

Although a log file output path is specified as a configuration property into a SpeechRecognizer or other SDK object, SDK logging is a singleton, process-wide facility with no concept of individual instances. You can think of this as the SpeechRecognizer constructor (or similar) implicitly calling a static and internal "Configure Global Logging" routine with the property data available in the corresponding SpeechConfig.

This means that you can't, as an example, configure six parallel recognizers to output simultaneously to six separate files. Instead, the latest recognizer created will configure the global logging instance to output to the file specified in its configuration properties and all SDK logging will be emitted to that file.

This also means that the lifetime of the object that configured logging isn't tied to the duration of logging. Logging will not stop in response to the release of an SDK object and will continue as long as no new logging configuration is provided. Once started, process-wide logging may be stopped by setting the log file path to an empty string when creating a new object.

To reduce potential confusion when configuring logging for multiple instances, it may be useful to abstract control of logging from objects doing real work. An example pair of helper routines:

void EnableSpeechSdkLogging(const char* relativePath)
	auto configForLogging = SpeechConfig::FromSubscription("unused_key", "unused_region");
	configForLogging->SetProperty(PropertyId::Speech_LogFilename, relativePath);
	auto emptyAudioConfig = AudioConfig::FromStreamInput(AudioInputStream::CreatePushStream());
	auto temporaryRecognizer = SpeechRecognizer::FromConfig(configForLogging, emptyAudioConfig);

void DisableSpeechSdkLogging()

Next steps