Event telemetry: Application Insights data model

You can create event telemetry items (in Application Insights) to represent an event that occurred in your application. Typically it is a user interaction such as button click or order checkout. It can also be an application life cycle event like initialization or configuration update.

Semantically, events may or may not be correlated to requests. However, if used properly, event telemetry is more important than requests or traces. Events represent business telemetry and should be a subject to separate, less aggressive sampling.


Event name. To allow proper grouping and useful metrics, restrict your application so that it generates a small number of separate event names. For example, don't use a separate name for each generated instance of an event.

Max length: 512 characters

Custom properties

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

  • Maximum key length: 150
  • Maximum value length: 8,192

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

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