Configuring the Application Insights SDK with ApplicationInsights.config or .xml

The Application Insights .NET SDK consists of many NuGet packages. The core package provides the API for sending telemetry to the Application Insights. More packages provide telemetry modules and initializers for automatically tracking telemetry from your application and its context. By adjusting the configuration file, you can enable or disable Telemetry Modules and initializers, and set parameters for some of them.

The configuration file is named ApplicationInsights.config or ApplicationInsights.xml, depending on the type of your application. It's automatically added to your project when you install most versions of the SDK. By default, when using the automated experience from the Visual Studio template projects that support Add > Application Insights Telemetry, the ApplicationInsights.config file is created in the project root folder and when compiled is copied to the bin folder. It's also added to a web app by Status Monitor on an IIS server. The configuration file is ignored if extension for Azure website or extension for Azure VM and virtual machine scale set is used.

There isn't an equivalent file to control the SDK in a web page.

This document describes the sections you see in the configuration file, how they control the components of the SDK, and which NuGet packages load those components.


ApplicationInsights.config and .xml instructions do not apply to the .NET Core SDK. For configuring .NET Core applications, follow this guide.

Telemetry Modules (ASP.NET)

Each Telemetry Module collects a specific type of data and uses the core API to send the data. The modules are installed by different NuGet packages, which also add the required lines to the .config file.

There's a node in the configuration file for each module. To disable a module, delete the node or comment it out.

Dependency Tracking

Dependency tracking collects telemetry about calls your app makes to databases and external services and databases. To allow this module to work in an IIS server, you need to install Status Monitor.

You can also write your own dependency tracking code using the TrackDependency API.

Dependencies can be auto-collected without modifying your code by using agent-based (codeless) attach. To use it in Azure web apps, enable the Application Insights extension. To use it in Azure VM or Azure virtual machine scale set enable the Application Monitoring extension for VM and virtual machine scale set.

Performance collector

Collects system performance counters such as CPU, memory, and network load from IIS installations. You can specify which counters to collect, including performance counters you have set up yourself.

Application Insights Diagnostics Telemetry

The DiagnosticsTelemetryModule reports errors in the Application Insights instrumentation code itself. For example, if the code can't access performance counters or if an ITelemetryInitializer throws an exception. Trace telemetry tracked by this module appears in the Diagnostic Search.

* `Microsoft.ApplicationInsights.Extensibility.Implementation.Tracing.DiagnosticsTelemetryModule`
* [Microsoft.ApplicationInsights]( NuGet package. If you only install this package, the ApplicationInsights.config file is not automatically created.

Developer Mode

DeveloperModeWithDebuggerAttachedTelemetryModule forces the Application Insights TelemetryChannel to send data immediately, one telemetry item at a time, when a debugger is attached to the application process. This design reduces the amount of time between the moment when your application tracks telemetry and when it appears on the Application Insights portal. It causes significant overhead in CPU and network bandwidth.

Web Request Tracking

Reports the response time and result code of HTTP requests.

Exception tracking

ExceptionTrackingTelemetryModule tracks unhandled exceptions in your web app. See Failures and exceptions.

  • Microsoft.ApplicationInsights.Web.ExceptionTrackingTelemetryModule
  • Microsoft.ApplicationInsights.Web NuGet package
  • Microsoft.ApplicationInsights.WindowsServer.UnobservedExceptionTelemetryModule - tracks unobserved task exceptions
  • Microsoft.ApplicationInsights.WindowsServer.UnhandledExceptionTelemetryModule - tracks unhandled exceptions for worker roles, Windows services, and console applications.
  • Application Insights Windows Server NuGet package.

EventSource Tracking

EventSourceTelemetryModule allows you to configure EventSource events to be sent to Application Insights as traces. For information on tracking EventSource events, see Using EventSource Events.

ETW Event Tracking

EtwCollectorTelemetryModule allows you to configure events from ETW providers to be sent to Application Insights as traces. For information on tracking ETW events, see Using ETW Events.


The Microsoft.ApplicationInsights package provides the core API of the SDK. The other Telemetry Modules use this API, and you can also use it to define your own telemetry.

  • No entry in ApplicationInsights.config.
  • Microsoft.ApplicationInsights NuGet package. If you just install this NuGet, no .config file is generated.

Telemetry Channel

The telemetry channel manages buffering and transmission of telemetry to the Application Insights service.

  • Microsoft.ApplicationInsights.WindowsServer.TelemetryChannel.ServerTelemetryChannel is the default channel for web applications. It buffers data in memory, and employs retry mechanisms and local disk storage for more reliable telemetry delivery.
  • Microsoft.ApplicationInsights.InMemoryChannel is a lightweight telemetry channel, which is used if no other channel is configured.

Telemetry Initializers (ASP.NET)

Telemetry Initializers set context properties that are sent along with every item of telemetry.

You can write your own initializers to set context properties.

The standard initializers are all set either by the Web or WindowsServer NuGet packages:

  • AccountIdTelemetryInitializer sets the AccountId property.

  • AuthenticatedUserIdTelemetryInitializer sets the AuthenticatedUserId property as set by the JavaScript SDK.

  • AzureRoleEnvironmentTelemetryInitializer updates the RoleName and RoleInstance properties of the Device context for all telemetry items with information extracted from the Azure runtime environment.

  • BuildInfoConfigComponentVersionTelemetryInitializer updates the Version property of the Component context for all telemetry items with the value extracted from the BuildInfo.config file produced by MS Build.

  • ClientIpHeaderTelemetryInitializer updates Ip property of the Location context of all telemetry items based on the X-Forwarded-For HTTP header of the request.

  • DeviceTelemetryInitializer updates the following properties of the Device context for all telemetry items.

    • Type is set to "PC"
    • Id is set to the domain name of the computer where the web application is running.
    • OemName is set to the value extracted from the Win32_ComputerSystem.Manufacturer field using WMI.
    • Model is set to the value extracted from the Win32_ComputerSystem.Model field using WMI.
    • NetworkType is set to the value extracted from the NetworkInterface.
    • Language is set to the name of the CurrentCulture.
  • DomainNameRoleInstanceTelemetryInitializer updates the RoleInstance property of the Device context for all telemetry items with the domain name of the computer where the web application is running.

  • OperationNameTelemetryInitializer updates the Name property of the RequestTelemetry and the Name property of the Operation context of all telemetry items based on the HTTP method, as well as names of ASP.NET MVC controller and action invoked to process the request.

  • OperationIdTelemetryInitializer or OperationCorrelationTelemetryInitializer updates the Operation.Id context property of all telemetry items tracked while handling a request with the automatically generated RequestTelemetry.Id.

  • SessionTelemetryInitializer updates the Id property of the Session context for all telemetry items with value extracted from the ai_session cookie generated by the ApplicationInsights JavaScript instrumentation code running in the user's browser.

  • SyntheticTelemetryInitializer or SyntheticUserAgentTelemetryInitializer updates the User, Session, and Operation contexts properties of all telemetry items tracked when handling a request from a synthetic source, such as an availability test or search engine bot. By default, Metrics Explorer doesn't display synthetic telemetry.

    The <Filters> set identifying properties of the requests.

  • UserTelemetryInitializer updates the Id and AcquisitionDate properties of User context for all telemetry items with values extracted from the ai_user cookie generated by the Application Insights JavaScript instrumentation code running in the user's browser.

  • WebTestTelemetryInitializer sets the user ID, session ID, and synthetic source properties for HTTP requests that come from availability tests. The <Filters> set identifying properties of the requests.

For .NET applications running in Service Fabric, you can include the Microsoft.ApplicationInsights.ServiceFabric NuGet package. This package includes a FabricTelemetryInitializer, which adds Service Fabric properties to telemetry items. For more information, see the GitHub page about the properties added by this NuGet package.

Telemetry Processors (ASP.NET)

Telemetry Processors can filter and modify each telemetry item just before it's sent from the SDK to the portal.

You can write your own Telemetry Processors.

Adaptive sampling Telemetry Processor (from 2.0.0-beta3)

This functionality is enabled by default. If your app sends considerable telemetry, this processor removes some of it.

      <Add Type="Microsoft.ApplicationInsights.WindowsServer.TelemetryChannel.AdaptiveSamplingTelemetryProcessor, Microsoft.AI.ServerTelemetryChannel">

The parameter provides the target that the algorithm tries to achieve. Each instance of the SDK works independently, so if your server is a cluster of several machines, the actual volume of telemetry will be multiplied accordingly.

Learn more about sampling.

Fixed-rate sampling Telemetry Processor (from 2.0.0-beta1)

There's also a standard sampling Telemetry Processor (from 2.0.1):

     <Add Type="Microsoft.ApplicationInsights.WindowsServer.TelemetryChannel.SamplingTelemetryProcessor, Microsoft.AI.ServerTelemetryChannel">

     <!-- Set a percentage close to 100/N where N is an integer. -->
     <!-- E.g. 50 (=100/2), 33.33 (=100/3), 25 (=100/4), 20, 1 (=100/100), 0.1 (=100/1000) -->


Connection string code samples



On March 31, 2025, support for instrumentation key ingestion will end. Instrumentation key ingestion will continue to work, but we'll no longer provide updates or support for the feature. Transition to connection strings to take advantage of new capabilities.

This setting determines the Application Insights resource in which your data appears. Typically you create a separate resource, with a separate key, for each of your applications.

If you want to set the key dynamically - for example if you want to send results from your application to different resources - you can omit the key from the configuration file, and set it in code instead.

To set the key for all instances of TelemetryClient, including standard Telemetry Modules. Do this step in an initialization method, such as global.aspx.cs in an ASP.NET service:

using Microsoft.ApplicationInsights.Extensibility;
using Microsoft.ApplicationInsights;

    protected void Application_Start()
        TelemetryConfiguration configuration = TelemetryConfiguration.CreateDefault();
        configuration.InstrumentationKey = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx";
        var telemetryClient = new TelemetryClient(configuration);

If you just want to send a specific set of events to a different resource, you can set the key for a specific TelemetryClient:

    var tc = new TelemetryClient();
    tc.Context.InstrumentationKey = "----- my key ----";
    // ...

To get a new key, create a new resource in the Application Insights portal.

ApplicationId Provider

Available starting in v2.6.0

The purpose of this provider is to look up an Application ID based on an Instrumentation Key. The Application ID is included in RequestTelemetry and DependencyTelemetry and used to determine Correlation in the Portal.

This functionality is available by setting TelemetryConfiguration.ApplicationIdProvider either in code or in config.

Interface: IApplicationIdProvider

public interface IApplicationIdProvider
    bool TryGetApplicationId(string instrumentationKey, out string applicationId);

We provide two implementations in the Microsoft.ApplicationInsights sdk: ApplicationInsightsApplicationIdProvider and DictionaryApplicationIdProvider.


This wrapper is for our Profile API. It will throttle requests and cache results.

This provider is added to your config file when you install either Microsoft.ApplicationInsights.DependencyCollector or Microsoft.ApplicationInsights.Web

This class has an optional property ProfileQueryEndpoint. By default it's set to{0}/appId. If you need to configure a proxy for this configuration, we recommend proxying the base address and including "/api/profiles/{0}/appId". A '{0}' is substituted at runtime per request with the Instrumentation Key.

Example Configuration via ApplicationInsights.config:

    <ApplicationIdProvider Type="Microsoft.ApplicationInsights.Extensibility.Implementation.ApplicationId.ApplicationInsightsApplicationIdProvider, Microsoft.ApplicationInsights">

Example Configuration via code:

TelemetryConfiguration.Active.ApplicationIdProvider = new ApplicationInsightsApplicationIdProvider();


This static provider relies on your configured Instrumentation Key / Application ID pairs.

This class has a property Defined, which is a Dictionary<string,string> of Instrumentation Key to Application ID pairs.

This class has an optional property Next, which can be used to configure another provider to use when an Instrumentation Key is requested that doesn't exist in your configuration.

Example Configuration via ApplicationInsights.config:

    <ApplicationIdProvider Type="Microsoft.ApplicationInsights.Extensibility.Implementation.ApplicationId.DictionaryApplicationIdProvider, Microsoft.ApplicationInsights">
            <Type key="InstrumentationKey_1" value="ApplicationId_1"/>
            <Type key="InstrumentationKey_2" value="ApplicationId_2"/>
        <Next Type="Microsoft.ApplicationInsights.Extensibility.Implementation.ApplicationId.ApplicationInsightsApplicationIdProvider, Microsoft.ApplicationInsights" />

Example Configuration via code:

TelemetryConfiguration.Active.ApplicationIdProvider = new DictionaryApplicationIdProvider{
 Defined = new Dictionary<string, string>
        {"InstrumentationKey_1", "ApplicationId_1"},
        {"InstrumentationKey_2", "ApplicationId_2"}

Configure snapshot collection for ASP.NET applications

Configure snapshot collection for ASP.NET applications

Next steps

Learn more about the API.