Request telemetry: Application Insights data model

A request telemetry item (in Application Insights) represents the logical sequence of execution triggered by an external request to your application. Every request execution is identified by unique ID and url containing all the execution parameters. You can group requests by logical name and define the source of this request. Code execution can result in success or fail and has a certain duration. Both success and failure executions may be grouped further by resultCode. Start time for the request telemetry defined on the envelope level.

Request telemetry supports the standard extensibility model using custom properties and measurements.


Name of the request represents code path taken to process the request. Low cardinality value to allow better grouping of requests. For HTTP requests it represents the HTTP method and URL path template like GET /values/{id} without the actual id value.

Application Insights web SDK sends request name "as is" with regards to letter case. Grouping on UI is case-sensitive so GET /Home/Index is counted separately from GET /home/INDEX even though often they result in the same controller and action execution. The reason for that is that urls in general are case-sensitive. You may want to see if all 404 happened for the urls typed in uppercase. You can read more on request name collection by ASP.Net Web SDK in the blog post.

Max length: 1024 characters


Identifier of a request call instance. Used for correlation between request and other telemetry items. ID should be globally unique. For more information, see correlation page.

Max length: 128 characters


Request URL with all query string parameters.

Max length: 2048 characters


Source of the request. Examples are the instrumentation key of the caller or the ip address of the caller. For more information, see correlation page.

Max length: 1024 characters


Request duration in format: DD.HH:MM:SS.MMMMMM. Must be positive and less than 1000 days. This field is required as request telemetry represents the operation with the beginning and the end.

Response code

Result of a request execution. HTTP status code for HTTP requests. It may be HRESULT value or exception type for other request types.

Max length: 1024 characters


Indication of successful or unsuccessful call. This field is required. When not set explicitly to false - request considered to be successful. Set this value to false if operation was interrupted by exception or returned error result code.

For the web applications, Application Insights define request as failed when the response code is less the 400 or equal to 401. However there are cases when this default mapping does not match the semantic of the application. Response code 404 may indicate "no records", which can be part of regular flow. It also may indicate a broken link. For the broken links, you can even implement more advanced logic. You can mark broken links as failures only when those links are located on the same site by analyzing url referrer. Or mark them as failures when accessed from the company's mobile application. Similarly 301 and 302 indicates failure when accessed from the client that doesn't support redirect.

Partially accepted content 206 may indicate a failure of an overall request. For instance, Application Insights endpoint receives a batch of telemetry items as a single request. It returns 206 when some items in the batch were not processed successfully. Increasing rate of 206 indicates a problem that needs to be investigated. Similar logic applies to 207 Multi-Status where the success may be the worst of separate response codes.

You can read more on request result code and status code in the blog post.

Custom properties

Name-value collection of custom properties. This collection is used to extend standard telemetry with the custom dimensions. Examples are deployment slot that produced telemetry or telemetry-item specific property like order number.

Max key length: 150 Max value length: 8192

Custom measurements

Collection of custom measurements. Use this collection to report named measurement associated with the telemetry item. Typical use cases are:

  • the size of Dependency Telemetry payload
  • the number of queue items processed by Request Telemetry
  • time that customer took to complete the step in wizard step completion Event Telemetry.

You can query custom measurements in Application Analytics:

| where customMeasurements != ""
| summarize avg(todouble(customMeasurements["Completion Time"]) * itemCount)


Custom measurements are associated with the telemetry item they belong to. They are subject to sampling with the telemetry item containing those measurements. To track a measurement that has a value independent from other telemetry types, use Metric telemetry.

Max key length: 150

Next steps