Monitor Azure App Service performance

Enabling monitoring on your ASP.NET, ASP.NET Core, and Node.js based web applications running on Azure App Services is now easier than ever. Whereas previously you needed to manually install a site extension, the latest extension/agent is now built into the app service image by default. This article will walk you through enabling Application Insights monitoring as well as provide preliminary guidance for automating the process for large-scale deployments.


Manually adding an Application Insights site extension via Development Tools > Extensions is deprecated. This method of extension installation was dependent on manual updates for each new version. The latest stable release of the extension is now preinstalled as part of the App Service image. The files are located in d:\Program Files (x86)\SiteExtensions\ApplicationInsightsAgent and are automatically updated with each stable release. If you follow the agent based instructions to enable monitoring below, it will automatically remove the deprecated extension for you.

Enable Application Insights

There are two ways to enable application monitoring for Azure App Services hosted applications:

  • Agent-based application monitoring (ApplicationInsightsAgent).

    • This method is the easiest to enable, and no advanced configuration is required. It is often referred to as "runtime" monitoring. For Azure App Services we recommend at a minimum enabling this level of monitoring, and then based on your specific scenario you can evaluate whether more advanced monitoring through manual instrumentation is needed.
  • Manually instrumenting the application through code by installing the Application Insights SDK.


If both agent-based monitoring and manual SDK-based instrumentation is detected, only the manual instrumentation settings will be honored. This is to prevent duplicate data from being sent. To learn more about this, check out the troubleshooting section below.

Enable agent-based monitoring


The combination of APPINSIGHTS_JAVASCRIPT_ENABLED and urlCompression is not supported. For more info see the explanation in the troubleshooting section.

  1. Select Application Insights in the Azure control panel for your app service.

    Under Settings, choose Application Insights

    • Choose to create a new resource, unless you already set up an Application Insights resource for this application.


      When you click OK to create the new resource you will be prompted to Apply monitoring settings. Selecting Continue will link your new Application Insights resource to your app service, doing so will also trigger a restart of your app service.

      Instrument your web app

  2. After specifying which resource to use, you can choose how you want application insights to collect data per platform for your application. ASP.NET app monitoring is on-by-default with two different levels of collection.

    Screenshot shows the Application Insights site extensions page with Create new resource selected.

Below is a summary of data collected for each route:

Data ASP.NET Basic Collection ASP.NET Recommended collection
Adds CPU, memory, and I/O usage trends Yes Yes
Collects usage trends, and enables correlation from availability results to transactions Yes Yes
Collects exceptions unhandled by the host process Yes Yes
Improves APM metrics accuracy under load, when sampling is used Yes Yes
Correlates micro-services across request/dependency boundaries No (single-instance APM capabilities only) Yes
  1. To configure settings like sampling, which you could previously control via the applicationinsights.config file you can now interact with those same settings via Application settings with a corresponding prefix.

    • For example, to change the initial sampling percentage, you can create an Application setting of: MicrosoftAppInsights_AdaptiveSamplingTelemetryProcessor_InitialSamplingPercentage and a value of 100.

    • For the list of supported adaptive sampling telemetry processor settings, you can consult the code and associated documentation.

Enable client-side monitoring

Client-side monitoring is opt-in for ASP.NET. To enable client-side monitoring:

  • Settings > Configuration
    • Under Application settings, create a new application setting:


      Value: true

    • Save the settings and Restart your app.

To disable client-side monitoring either remove the associated key value pair from the Application settings, or set the value to false.

Automate monitoring

In order to enable telemetry collection with Application Insights, only the Application settings need to be set:

App Service Application Settings with available Application Insights settings

Application settings definitions

App setting name Definition Value
ApplicationInsightsAgent_EXTENSION_VERSION Main extension, which controls runtime monitoring. ~2
XDT_MicrosoftApplicationInsights_Mode In default mode only, essential features are enabled in order to insure optimal performance. default or recommended.
InstrumentationEngine_EXTENSION_VERSION Controls if the binary-rewrite engine InstrumentationEngine will be turned on. This setting has performance implications and impacts cold start/startup time. ~1
XDT_MicrosoftApplicationInsights_BaseExtensions Controls if SQL & Azure table text will be captured along with the dependency calls. Performance warning: application cold start up time will be affected. This setting requires the InstrumentationEngine. ~1
XDT_MicrosoftApplicationInsights_PreemptSdk For ASP.NET Core apps only. Enables Interop (interoperation) with Application Insights SDK. Loads the extension side-by-side with the SDK and uses it to send telemetry (disables the Application Insights SDK). 1

App Service Application settings with Azure Resource Manager

Application settings for App Services can be managed and configured with Azure Resource Manager templates. This method can be used when deploying new App Service resources with Azure Resource Manager automation, or for modifying the settings of existing resources.

The basic structure of the application settings JSON for an app service is below:

      "resources": [
          "name": "appsettings",
          "type": "config",
          "apiVersion": "2015-08-01",
          "dependsOn": [
            "[resourceId('Microsoft.Web/sites', variables('webSiteName'))]"
          "tags": {
            "displayName": "Application Insights Settings"
          "properties": {
            "key1": "value1",
            "key2": "value2"

For an example of an Azure Resource Manager template with Application settings configured for Application Insights, this template can be helpful, specifically the section starting on line 238.

To create an Azure Resource Manager template with all the default Application Insights settings configured, begin the process as if you were going to create a new Web App with Application Insights enabled.

Select Automation options

App Service web app creation menu

This option generates the latest Azure Resource Manager template with all required settings configured.

App Service web app template

Below is a sample, replace all instances of AppMonitoredSite with your site name:

    "resources": [
            "name": "[parameters('name')]",
            "type": "Microsoft.Web/sites",
            "properties": {
                "siteConfig": {
                    "appSettings": [
                            "name": "APPINSIGHTS_INSTRUMENTATIONKEY",
                            "value": "[reference('microsoft.insights/components/AppMonitoredSite', '2015-05-01').InstrumentationKey]"
                            "name": "APPLICATIONINSIGHTS_CONNECTION_STRING",
                            "value": "[reference('microsoft.insights/components/AppMonitoredSite', '2015-05-01').ConnectionString]"
                            "name": "ApplicationInsightsAgent_EXTENSION_VERSION",
                            "value": "~2"
                "name": "[parameters('name')]",
                "serverFarmId": "[concat('/subscriptions/', parameters('subscriptionId'),'/resourcegroups/', parameters('serverFarmResourceGroup'), '/providers/Microsoft.Web/serverfarms/', parameters('hostingPlanName'))]",
                "hostingEnvironment": "[parameters('hostingEnvironment')]"
            "dependsOn": [
                "[concat('Microsoft.Web/serverfarms/', parameters('hostingPlanName'))]",
            "apiVersion": "2016-03-01",
            "location": "[parameters('location')]"
            "apiVersion": "2016-09-01",
            "name": "[parameters('hostingPlanName')]",
            "type": "Microsoft.Web/serverfarms",
            "location": "[parameters('location')]",
            "properties": {
                "name": "[parameters('hostingPlanName')]",
                "workerSizeId": "[parameters('workerSize')]",
                "numberOfWorkers": "1",
                "hostingEnvironment": "[parameters('hostingEnvironment')]"
            "sku": {
                "Tier": "[parameters('sku')]",
                "Name": "[parameters('skuCode')]"
            "apiVersion": "2015-05-01",
            "name": "AppMonitoredSite",
            "type": "microsoft.insights/components",
            "location": "West US 2",
            "properties": {
                "ApplicationId": "[parameters('name')]",
                "Request_Source": "IbizaWebAppExtensionCreate"
    "parameters": {
        "name": {
            "type": "string"
        "hostingPlanName": {
            "type": "string"
        "hostingEnvironment": {
            "type": "string"
        "location": {
            "type": "string"
        "sku": {
            "type": "string"
        "skuCode": {
            "type": "string"
        "workerSize": {
            "type": "string"
        "serverFarmResourceGroup": {
            "type": "string"
        "subscriptionId": {
            "type": "string"
    "$schema": "",
    "contentVersion": ""

Enabling through PowerShell

In order to enable the application monitoring through PowerShell, only the underlying application settings need to be changed. Below is a sample, which enables application monitoring for a website called "AppMonitoredSite" in the resource group "AppMonitoredRG", and configures data to be sent to the "012345678-abcd-ef01-2345-6789abcd" instrumentation key.


This article has been updated to use the Azure Az PowerShell module. The Az PowerShell module is the recommended PowerShell module for interacting with Azure. To get started with the Az PowerShell module, see Install Azure PowerShell. To learn how to migrate to the Az PowerShell module, see Migrate Azure PowerShell from AzureRM to Az.

$app = Get-AzWebApp -ResourceGroupName "AppMonitoredRG" -Name "AppMonitoredSite" -ErrorAction Stop
$newAppSettings = @{} # case-insensitive hash map
$app.SiteConfig.AppSettings | %{$newAppSettings[$_.Name] = $_.Value} # preserve non Application Insights application settings.
$newAppSettings["APPINSIGHTS_INSTRUMENTATIONKEY"] = "012345678-abcd-ef01-2345-6789abcd"; # set the Application Insights instrumentation key
$newAppSettings["APPLICATIONINSIGHTS_CONNECTION_STRING"] = "InstrumentationKey=012345678-abcd-ef01-2345-6789abcd"; # set the Application Insights connection string
$newAppSettings["ApplicationInsightsAgent_EXTENSION_VERSION"] = "~2"; # enable the ApplicationInsightsAgent
$app = Set-AzWebApp -AppSettings $newAppSettings -ResourceGroupName $app.ResourceGroup -Name $app.Name -ErrorAction Stop

Upgrade monitoring extension/agent

Upgrading from versions 2.8.9 and up

Upgrading from version 2.8.9 happens automatically, without any additional actions. The new monitoring bits are delivered in the background to the target app service, and on application restart they will be picked up.

To check which version of the extension you are running visit

Screenshot of url path

Upgrade from versions 1.0.0 - 2.6.5

Starting with version 2.8.9 the pre-installed site extension is used. If you are an earlier version, you can update via one of two ways:

  • Upgrade by enabling via the portal. (Even if you have the Application Insights extension for Azure App Service installed, the UI shows only Enable button. Behind the scenes, the old private site extension will be removed.)

  • Upgrade through PowerShell:

    1. Set the application settings to enable the pre-installed site extension ApplicationInsightsAgent. See Enabling through PowerShell.
    2. Manually remove the private site extension named Application Insights extension for Azure App Service.

If the upgrade is done from a version prior to 2.5.1, check that the ApplicationInsigths dlls are removed from the application bin folder see troubleshooting steps.


Below is our step-by-step troubleshooting guide for extension/agent based monitoring for ASP.NET and ASP.NET Core based applications running on Azure App Services.


The recommended approach to monitor Java applications is to use the auto-instrumentation without changing the code. Please follow the guidelines for Application Insights Java 3.0 agent.

  1. Check that the application is monitored via ApplicationInsightsAgent.

    • Check that ApplicationInsightsAgent_EXTENSION_VERSION app setting is set to a value of "~2".
  2. Ensure that the application meets the requirements to be monitored.

    • Browse to

    Screenshot of https://yoursitename.scm.azurewebsites/applicationinsights results page

    • Confirm that the Application Insights Extension Status is Pre-Installed Site Extension, version, is running.

    • If it is not running, follow the enable Application Insights monitoring instructions

    • Confirm that the status source exists and looks like: Status source D:\home\LogFiles\ApplicationInsights\status\status_RD0003FF0317B6_4248_1.json

      • If a similar value is not present, it means the application is not currently running or is not supported. To ensure that the application is running, try manually visiting the application url/application endpoints, which will allow the runtime information to become available.
    • Confirm that IKeyExists is true

      • If it is false, add APPINSIGHTS_INSTRUMENTATIONKEY and APPLICATIONINSIGHTS_CONNECTION_STRING with your ikey guid to your application settings.
    • Confirm that there are no entries for AppAlreadyInstrumented, AppContainsDiagnosticSourceAssembly, and AppContainsAspNetTelemetryCorrelationAssembly.

      • If any of these entries exist, remove the following packages from your application: Microsoft.ApplicationInsights, System.Diagnostics.DiagnosticSource, and Microsoft.AspNet.TelemetryCorrelation.
      • For ASP.NET Core apps only: in case your application refers to any Application Insights packages, for example if you have previously instrumented (or attempted to instrument) your app with the ASP.NET Core SDK, enabling the App Service integration may not take effect and the data may not appear in Application Insights. To fix the issue, in portal turn on "Interop with Application Insights SDK" and you will start seeing the data in Application Insights


      This functionality is in preview

      Enable the setting the existing app

      The data is now going to be sent using codeless approach even if Application Insights SDK was originally used or attempted to be used.


      If the application used Application Insights SDK to send any telemetry, such telemetry will be disabled – in other words, custom telemetry - if any, such as for example any Track*() methods, and any custom settings, such as sampling, will be disabled.

PHP and WordPress are not supported

PHP and WordPress sites are not supported. There is currently no officially supported SDK/agent for server-side monitoring of these workloads. However, manually instrumenting client-side transactions on a PHP or WordPress site by adding the client-side JavaScript to your web pages can be accomplished by using the JavaScript SDK.

The table below provides a more detailed explanation of what these values mean, their underlying causes, and recommended fixes:

Problem Value Explanation Fix
AppAlreadyInstrumented:true This value indicates that the extension detected that some aspect of the SDK is already present in the Application, and will back-off. It can be due to a reference to System.Diagnostics.DiagnosticSource, Microsoft.AspNet.TelemetryCorrelation, or Microsoft.ApplicationInsights Remove the references. Some of these references are added by default from certain Visual Studio templates, and older versions of Visual Studio may add references to Microsoft.ApplicationInsights.
AppAlreadyInstrumented:true If the application is targeting ASP.NET Core 2.1 or 2.2, this value indicates that the extension detected that some aspect of the SDK is already present in the Application, and will back-off Customers on .NET Core 2.1,2.2 are recommended to use Microsoft.AspNetCore.App meta-package instead. In addition, turn on "Interop with Application Insights SDK" in portal (see the instructions above).
AppAlreadyInstrumented:true This value can also be caused by the presence of the above dlls in the app folder from a previous deployment. Clean the app folder to ensure that these dlls are removed. Check both your local app's bin directory, and the wwwroot directory on the App Service. (To check the wwwroot directory of your App Service web app: Advanced Tools (Kudu) > Debug console > CMD > home\site\wwwroot).
AppContainsAspNetTelemetryCorrelationAssembly: true This value indicates that extension detected references to Microsoft.AspNet.TelemetryCorrelation in the application, and will back-off. Remove the reference.
AppContainsDiagnosticSourceAssembly**:true This value indicates that extension detected references to System.Diagnostics.DiagnosticSource in the application, and will back-off. For ASP.NET remove the reference.
IKeyExists:false This value indicates that the instrumentation key is not present in the AppSetting, APPINSIGHTS_INSTRUMENTATIONKEY. Possible causes: The values may have been accidentally removed, forgot to set the values in automation script, etc. Make sure the setting is present in the App Service application settings.

APPINSIGHTS_JAVASCRIPT_ENABLED and urlCompression is not supported

If you use APPINSIGHTS_JAVASCRIPT_ENABLED=true in cases where content is encoded, you might get errors like:

  • 500 URL rewrite error
  • 500.53 URL rewrite module error with message Outbound rewrite rules cannot be applied when the content of the HTTP response is encoded ('gzip').

This is due to the APPINSIGHTS_JAVASCRIPT_ENABLED application setting being set to true and content-encoding being present at the same time. This scenario is not supported yet. The workaround is to remove APPINSIGHTS_JAVASCRIPT_ENABLED from your application settings. Unfortunately this means that if client/browser-side JavaScript instrumentation is still required, manual SDK references are needed for your webpages. Please follow the instructions for manual instrumentation with the JavaScript SDK.

For the latest information on the Application Insights agent/extension, check out the release notes.

Default website deployed with web apps does not support automatic client-side monitoring

When you create a web app with the ASP.NET or ASP.NET Core runtimes in Azure App Services it deploys a single static HTML page as a starter website. The static webpage also loads a ASP.NET managed web part in IIS. This allows for testing codeless server-side monitoring, but does not support automatic client-side monitoring.

If you wish to test out codeless server and client-side monitoring for ASP.NET or ASP.NET Core in a Azure App Services web app we recommend following the official guides for creating a ASP.NET Core web app and creating an ASP.NET Framework web app and then use the instructions in the current article to enable monitoring.

Connection string and instrumentation key

When codeless monitoring is being used, only the connection string is required. However, we still recommend setting the instrumentation key to preserve backwards compatibility with older versions of the SDK when manual instrumentation is being performed.

Difference between Standard Metrics from Application Insights vs Azure App Service metrics?

Application Insights collects telemetry for those requests which made it to the application. If the failure occurred in WebApps/IIS, and the request did not reach the user application, then Application Insights will not have any telemetry about it.

The duration for serverresponsetime calculated by Application Insights is not necessarily matching the server response time observed by Web Apps. This is because Application Insights only counts the duration when the request actual reaches user application. If the request is stuck/queued in IIS, that waiting time will be included in the Web App metrics, but not in Application Insights metrics.

Release notes

For the latest updates and bug fixes consult the release notes.

Next steps