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Logging article overhaul #36169

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Logging article overhaul
guardrex Sep 30, 2025
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guardrex Sep 30, 2025
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103 changes: 5 additions & 98 deletions aspnetcore/blazor/fundamentals/logging.md
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---
title: ASP.NET Core Blazor logging
author: guardrex
description: Learn about Blazor app logging, including configuration and how to write log messages from Razor components.
description: Learn about Blazor app logging, particularly in client-side logging scenarios.
monikerRange: '>= aspnetcore-3.1'
ms.author: wpickett
ms.custom: mvc
ms.date: 11/12/2024
ms.date: 09/29/2025
uid: blazor/fundamentals/logging
---
# ASP.NET Core Blazor logging
Expand All @@ -17,7 +17,9 @@ uid: blazor/fundamentals/logging
at the ends of lines to generate a bare return in block quote output.
-->

This article explains Blazor app logging, including configuration and how to write log messages from Razor components.
This article provides information on logging in Blazor apps, particularly in client-side logging scenarios.

For general ASP.NET Core logging guidance, including how to log from Razor components, see <xref:fundamentals/logging/index>.

## Configuration

Expand All @@ -38,101 +40,6 @@ When the app is configured in the project file to use implicit namespaces (`<Imp

Log levels conform to ASP.NET Core app log levels, which are listed in the API documentation at <xref:Microsoft.Extensions.Logging.LogLevel>.

## Razor component logging

:::moniker range="< aspnetcore-6.0"

The `using` directive for <xref:Microsoft.Extensions.Logging> is required to support [IntelliSense](/visualstudio/ide/using-intellisense) completions for APIs, such as <xref:Microsoft.Extensions.Logging.LoggerExtensions.LogWarning%2A> and <xref:Microsoft.Extensions.Logging.LoggerExtensions.LogError%2A>.

:::moniker-end

The following example:

* [Injects](xref:blazor/fundamentals/dependency-injection) an <xref:Microsoft.Extensions.Logging.ILogger> (`ILogger<Counter1>`) object to create a logger. The log's *category* is the fully qualified name of the component's type, `Counter`.
* Calls <xref:Microsoft.Extensions.Logging.LoggerExtensions.LogWarning%2A> to log at the <xref:Microsoft.Extensions.Logging.LogLevel.Warning> level.

`Counter1.razor`:

:::moniker range=">= aspnetcore-9.0"

:::code language="razor" source="~/../blazor-samples/9.0/BlazorSample_BlazorWebApp/Components/Pages/Counter1.razor":::

:::moniker-end

:::moniker range=">= aspnetcore-8.0 < aspnetcore-9.0"

:::code language="razor" source="~/../blazor-samples/8.0/BlazorSample_BlazorWebApp/Components/Pages/Counter1.razor":::

:::moniker-end

:::moniker range=">= aspnetcore-7.0 < aspnetcore-8.0"

:::code language="razor" source="~/../blazor-samples/7.0/BlazorSample_WebAssembly/Pages/logging/Counter1.razor":::

:::moniker-end

:::moniker range=">= aspnetcore-6.0 < aspnetcore-7.0"

:::code language="razor" source="~/../blazor-samples/6.0/BlazorSample_WebAssembly/Pages/logging/Counter1.razor":::

:::moniker-end

:::moniker range=">= aspnetcore-5.0 < aspnetcore-6.0"

:::code language="razor" source="~/../blazor-samples/5.0/BlazorSample_WebAssembly/Pages/logging/Counter1.razor":::

:::moniker-end

:::moniker range="< aspnetcore-5.0"

:::code language="razor" source="~/../blazor-samples/3.1/BlazorSample_WebAssembly/Pages/logging/Counter1.razor":::

:::moniker-end

The following example demonstrates logging with an <xref:Microsoft.Extensions.Logging.ILoggerFactory> in components.

`Counter2.razor`:

:::moniker range=">= aspnetcore-9.0"

:::code language="razor" source="~/../blazor-samples/9.0/BlazorSample_BlazorWebApp/Components/Pages/Counter2.razor":::

:::moniker-end

:::moniker range=">= aspnetcore-8.0 < aspnetcore-9.0"

:::code language="razor" source="~/../blazor-samples/8.0/BlazorSample_BlazorWebApp/Components/Pages/Counter2.razor":::

:::moniker-end

:::moniker range=">= aspnetcore-7.0 < aspnetcore-8.0"

:::code language="razor" source="~/../blazor-samples/7.0/BlazorSample_WebAssembly/Pages/logging/Counter2.razor":::

:::moniker-end

:::moniker range=">= aspnetcore-6.0 < aspnetcore-7.0"

:::code language="razor" source="~/../blazor-samples/6.0/BlazorSample_WebAssembly/Pages/logging/Counter2.razor":::

:::moniker-end

:::moniker range=">= aspnetcore-5.0 < aspnetcore-6.0"

:::code language="razor" source="~/../blazor-samples/5.0/BlazorSample_WebAssembly/Pages/logging/Counter2.razor":::

:::moniker-end

:::moniker range="< aspnetcore-5.0"

:::code language="razor" source="~/../blazor-samples/3.1/BlazorSample_WebAssembly/Pages/logging/Counter2.razor":::

:::moniker-end

## Server-side logging

For general ASP.NET Core logging guidance, see <xref:fundamentals/logging/index>.

## Client-side logging

Not every feature of [ASP.NET Core logging](xref:fundamentals/logging/index) is supported client-side. For example, client-side components don't have access to the client's file system or network, so writing logs to the client's physical or network storage isn't possible. When using a third-party logging service designed to work with single-page apps (SPAs), follow the service's security guidance. Keep in mind that every piece of data, including keys or secrets stored client-side are ***insecure*** and can be easily discovered by malicious users.
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