Monitor performance in web applications

Make sure your application is performing well, and find out quickly about any failures. Application Insights will tell you about any performance issues and exceptions, and help you find and diagnose the root causes.

Application Insights can monitor both Java and ASP.NET web applications and services, WCF services. They can be hosted on-premises, on virtual machines, or as Microsoft Azure websites.

On the client side, Application Insights can take telemetry from web pages and a wide variety of devices including iOS, Android and Windows Store apps.


We have made a new experience available for finding slow performing pages in your web application. If you don't have access to it, enable it by configuring your preview options with the Preview blade. Read about this new experience in Find and fix performance bottlenecks with the interactive Performance investigation.

Set up performance monitoring

If you haven't yet added Application Insights to your project (that is, if it doesn't have ApplicationInsights.config), choose one of these ways to get started:

Exploring performance metrics

In the Azure portal, browse to the Application Insights resource that you set up for your application. The overview blade shows basic performance data:

Click any chart to see more detail, and to see results for a longer period. For example, click the Requests tile and then select a time range:

Click through to more data and select a time range

Click a chart to choose which metrics it displays, or add a new chart and select its metrics:

Click a graph to choose metrics


Uncheck all the metrics to see the full selection that is available. The metrics fall into groups; when any member of a group is selected, only the other members of that group appear.

What does it all mean? Performance tiles and reports

There are various performance metrics you can get. Let's start with those that appear by default on the application blade.


The number of HTTP requests received in a specified period. Compare this with the results on other reports to see how your app behaves as the load varies.

HTTP requests include all GET or POST requests for pages, data, and images.

Click on the tile to get counts for specific URLs.

Average response time

Measures the time between a web request entering your application and the response being returned.

The points show a moving average. If there are a lot of requests, there might be some that deviate from the average without an obvious peak or dip in the graph.

Look for unusual peaks. In general, expect response time to rise with a rise in requests. If the rise is disproportionate, your app might be hitting a resource limit such as CPU or the capacity of a service it uses.

Click the tile to get times for specific URLs.

Slowest requests

Shows which requests might need performance tuning.

Failed requests

A count of requests that threw uncaught exceptions.

Click the tile to see the details of specific failures, and select an individual request to see its detail.

Only a representative sample of failures is retained for individual inspection.

Other metrics

To see what other metrics you can display, click a graph, and then deselect all the metrics to see the full available set. Click (i) to see each metric's definition.

Deselect all metrics to see the whole set

Selecting any metric disables the others that can't appear on the same chart.

Set alerts

To be notified by email of unusual values of any metric, add an alert. You can choose either to send the email to the account administrators, or to specific email addresses.

Set the resource before the other properties. Don't choose the webtest resources if you want to set alerts on performance or usage metrics.

Be careful to note the units in which you're asked to enter the threshold value.

I don't see the Add Alert button. - Is this a group account to which you have read-only access? Check with the account administrator.

Diagnosing issues

Here are a few tips for finding and diagnosing performance issues:

  • Set up web tests to be alerted if your web site goes down or responds incorrectly or slowly.
  • Compare the Request count with other metrics to see if failures or slow response are related to load.
  • Insert and search trace statements in your code to help pinpoint problems.
  • Monitor your Web app in operation with Live Metrics Stream.
  • Capture the state of your .Net application with Snapshot Debugger.

Find and fix performance bottlenecks with an interactive performance investigation

You can use the new Application Insights interactive performance investigation to locate areas of your Web app that are slowing down overall performance. You can quickly find specific pages that are slowing down, and use the Profiling tool to see if there is a correlation between these pages.

Create a list of slow performing pages

The first step for finding performance issues is to get a list of the slow responding pages. The screen shot below demonstrates using the Performance blade to get a list of potential pages to investigate further. You can quickly see from this page that there was a slow-down in the response time of the app at approximately 6:00 PM and again at approximately 10 PM. You can also see that the GET customer/details operation had some long running operations with a median response time of 507.05 milliseconds.

Application Insights Interactive Performance

Drill down on specific pages

Once you have a snapshot of your app's performance, you can get more details on specific slow-performing operations. Click on any operation in the list to see the details as shown below. From the chart you can see if the performance was based on a dependency. You can also see how many users experienced the various response times.

Application Insights operations blade

Drill down on a specific time period

After you have identified a point in time to investigate, drill down even further to look at the specific operations that might have caused the performance slow-down. When you click on a specific point in time you get the details of the page as shown below. In the example below you can see the operations listed for a given time period along with the server response codes and the operation duration. You also have the url for opening a TFS work item if you need to send this information to your development team.

Application Insights time slice

Drill down on a specific operation

After you have identified a point in time to investigate, drill down even further to look at the specific operations that might have caused the performance slow-down. Click on an operation from the list to see the details of the operation as shown below. In this example you can see that the operation failed, and Application Insights has provided the details of the exception the application threw. Again, you can easily create a TFS work item from this blade.

Application Insights operation blade

Next steps

Web tests - Have web requests sent to your application at regular intervals from around the world.

Capture and search diagnostic traces - Insert trace calls and sift through the results to pinpoint issues.

Usage tracking - Find out how people use your application.

Troubleshooting - and Q & A