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ASP.NET Core built-in metrics

This article is the entry point for the built-in metrics that ASP.NET Core produces using the System.Diagnostics.Metrics API. The metrics reference is organized into focused pages by topic. Use the following pages to find the instruments, attributes, and usage guidance for each area. For a listing of metrics based on the older EventCounters API, see Available counters.

For information on how to collect, report, enrich, and test with ASP.NET Core metrics, see ASP.NET Core metrics.

Metrics reference pages

Page Namespaces Example metrics
HTTP metrics Microsoft.AspNetCore.Hosting, Microsoft.AspNetCore.Routing, Microsoft.AspNetCore.RateLimiting, Microsoft.AspNetCore.HeaderParsing, Microsoft.AspNetCore.Server.Kestrel, Microsoft.AspNetCore.Http.Connections (SignalR) http.server.request.duration, aspnetcore.routing.match_attempts, kestrel.active_connections, signalr.server.active_connections
Diagnostics metrics Microsoft.AspNetCore.Diagnostics aspnetcore.diagnostics.exceptions
Blazor (Components) metrics Microsoft.AspNetCore.Components, Microsoft.AspNetCore.Components.Lifecycle, Microsoft.AspNetCore.Components.Server.Circuits aspnetcore.components.navigation, aspnetcore.components.circuit.active
Authentication and authorization metrics Microsoft.AspNetCore.Authorization, Microsoft.AspNetCore.Authentication aspnetcore.authorization.attempts, aspnetcore.authentication.challenges

The Blazor (Components) and authentication and authorization metrics pages describe metrics available in ASP.NET Core 10.0 or later. Select ASP.NET Core 10.0 (or a later version) with the version selector to view that content.

How metrics are grouped

Metrics are grouped by audience and topic. Because some namespaces don't map cleanly to a single topic, the following placement rules apply:

  • HTTP request handling, routing, rate limiting, header parsing, the Kestrel web server, and SignalR (Microsoft.AspNetCore.Http.Connections) are grouped together on the HTTP metrics page, because they all relate to serving HTTP and real-time connections.
  • Error handling middleware metrics are on the diagnostics metrics page.
  • Blazor (Components) metrics are grouped by their component, lifecycle, and server circuit namespaces.
  • Authentication, authorization, and Identity metrics are grouped together as security-related metrics.

How to read this reference

Each metric on the reference pages is documented with the following information:

  • Name: The metric (instrument) name.
  • Instrument Type: The kind of instrument, such as Counter, UpDownCounter, or Histogram.
  • Unit (UCUM): The unit of measurement, expressed using the Unified Code for Units of Measure (UCUM), for example s for seconds.
  • Attribute: The dimensions (tags) reported with the metric.
  • Presence: When the attribute is present, for example Always or only under specific conditions.
  • Usage: Example questions the metric helps answer.

For guidance on how to collect, report, enrich, and test with these metrics, see ASP.NET Core metrics.

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