Updates

Author: guardrex

aspnetcore/blazor/performance/index.md

@@ -1,11 +1,11 @@
 ---
 title: ASP.NET Core Blazor performance best practices
 author: guardrex
-description: Tips for increasing the performance of ASP.NET Core Blazor apps and avoiding common performance problems.
+description: Guidance on ASP.NET Core Blazor metrics and tracing, improving app performance, and avoiding common performance problems.
 monikerRange: '>= aspnetcore-3.1'
 ms.author: wpickett
 ms.custom: mvc
-ms.date: 04/16/2025
+ms.date: 06/08/2025
 uid: blazor/performance/index
 ---
 # ASP.NET Core Blazor performance best practices
@@ -24,3 +24,87 @@ Blazor is optimized for high performance in most realistic application UI scenar
 Ahead-of-time (AOT) compilation compiles a Blazor app's .NET code directly into native WebAssembly for direct execution by the browser. AOT-compiled apps result in larger apps that take longer to download, but AOT-compiled apps usually provide better runtime performance, especially for apps that execute CPU-intensive tasks. For more information, see <xref:blazor/tooling/webassembly#ahead-of-time-aot-compilation>.
 
 :::moniker-end
+
+:::moniker range=">= aspnetcore-10.0"
+
+## Metrics and tracing
+
+Metrics and tracing capabilities help you monitor and diagnose app performance, track user interactions, and understand component behavior in production environments.
+
+### Configuration
+
+To enable Blazor metrics and tracing in your app, configure [OpenTelemetry](https://github.com/open-telemetry/opentelemetry-dotnet) with the following meters and activity sources in the app's `Program` file where services are registered:
+
+```csharp
+builder.Services.ConfigureOpenTelemetryMeterProvider(meterProvider =>
+{
+    meterProvider.AddMeter("Microsoft.AspNetCore.Components");
+    meterProvider.AddMeter("Microsoft.AspNetCore.Components.Lifecycle");
+    meterProvider.AddMeter("Microsoft.AspNetCore.Components.Server.Circuits");
+});
+
+builder.Services.ConfigureOpenTelemetryTracerProvider(tracerProvider =>
+{
+    tracerProvider.AddSource("Microsoft.AspNetCore.Components");
+});
+```
+
+### Performance meters
+
+`Microsoft.AspNetCore.Components` meter:
+
+* `aspnetcore.components.navigation`: Tracks the total number of route changes in the app.
+* `aspnetcore.components.event_handler`: Measures the duration of processing browser events, including business logic.
+
+`Microsoft.AspNetCore.Components.Lifecycle` meter:
+
+* `aspnetcore.components.update_parameters`: Measures the duration of processing component parameters, including business logic.
+* `aspnetcore.components.render_diff`: Tracks the duration of rendering batches.
+
+`Microsoft.AspNetCore.Components.Server.Circuits` meter:
+
+In server-side Blazor apps, additional circuit-specific metrics include:
+
+* `aspnetcore.components.circuit.active`: Shows the number of active circuits currently in memory.
+* `aspnetcore.components.circuit.connected`: Tracks the number of circuits connected to clients.
+* `aspnetcore.components.circuit.duration`: Measures circuit lifetime duration and provides total circuit count.
+
+### Blazor tracing
+
+The new activity tracing capabilities use the `Microsoft.AspNetCore.Components` activity source and provide three main types of tracing activities: circuit lifecycle, navigation, and event handling.
+
+Circuit lifecycle tracing:
+
+`Microsoft.AspNetCore.Components.CircuitStart`: Traces circuit initialization with the format `Circuit {circuitId}`.
+
+* Tag: `aspnetcore.components.circuit.id`
+* Link: HTTP activity
+
+Navigation tracing:
+
+`Microsoft.AspNetCore.Components.RouteChange`: Tracks route changes with the format `Route {route} -> {componentType}`.
+
+* Tags
+  * `aspnetcore.components.circuit.id`
+  * `aspnetcore.components.route`
+  * `aspnetcore.components.type`
+* Links
+  * HTTP trace
+  * Circuit trace
+
+Event handling tracing:
+
+`Microsoft.AspNetCore.Components.HandleEvent`: Traces event handling with the format `Event {attributeName} -> {componentType}.{methodName}`.
+
+* Tags
+  * `aspnetcore.components.attribute.name`
+  * `aspnetcore.components.circuit.id`
+  * `aspnetcore.components.method`
+  * `aspnetcore.components.type`
+  * `error.type`
+* Links
+  * HTTP trace
+  * Circuit trace
+  * Router trace
+
+:::moniker-end

aspnetcore/release-notes/aspnetcore-10/includes/blazor.md

@@ -416,3 +416,9 @@ Blazor now provides an improved way to display a "Not Found" page when navigatin
 The Blazor project template now includes a `NotFound.razor` page by default. This page automatically renders whenever `NavigationManager.NotFound` is called in your app, making it easier to handle missing routes with a consistent user experience.
 
 For more information, see <xref:blazor/fundamentals/routing#not-found-responses>.
+
+### Metrics and tracing
+
+This release introduces comprehensive metrics and tracing capabilities for Blazor apps, providing detailed observability of the component lifecycle, navigation, event handling, and circuit management.
+
+For more information, see <xref:blazor/performance/index#metrics-and-tracing>.