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title author description monikerRange ms.author ms.custom ms.date uid
ASP.NET Core Blazor static files
guardrex
Learn how to configure and manage static files for Blazor apps.
>= aspnetcore-3.1
riande
mvc
06/11/2024
blazor/fundamentals/static-files

ASP.NET Core Blazor static files

[!INCLUDE]

This article describes Blazor app configuration for serving static files.

Static asset middleware

This section applies to server-side Blazor apps.

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

Serving static assets is managed by either of the two middlewares described in the following table.

Middleware API .NET Version Description
Map Static Assets MapStaticAssets .NET 9 or later Optimizes the delivery of static assets to clients.
Static Files xref:Microsoft.AspNetCore.Builder.StaticFileExtensions.UseStaticFiles%2A All .NET versions Serves static assets to clients without the optimizations of MapStaticAssets but useful for some tasks that MapStaticAssets isn't capable of managing.

Configure Map Static Assets Middleware by calling MapStaticAssets in the app's request processing pipeline, which performs the following:

MapStaticAssets operates by combining build and publish processes to collect information about the static assets in the app. This information is utilized by the runtime library to efficiently serve the static assets to browsers.

MapStaticAssets can replace xref:Microsoft.AspNetCore.Builder.StaticFileExtensions.UseStaticFiles%2A in most situations. However, MapStaticAssets is optimized for serving the assets from known locations in the app at build and publish time. If the app serves assets from other locations, such as disk or embedded resources, xref:Microsoft.AspNetCore.Builder.StaticFileExtensions.UseStaticFiles%2A should be used.

MapStaticAssets provides the following benefits not found with xref:Microsoft.AspNetCore.Builder.StaticFileExtensions.UseStaticFiles%2A:

  • Build-time compression for all the assets in the app: Gzip (Content-Encoding: gz) during development and Gzip with Brotli (Content-Encoding: br) during publish.
  • Content based ETags are generated for each static asset, which are Base64-encoded strings of the SHA-256 hashes of the static assets. This ensures that the browser only redownloads a file if its contents have changed.

Static File Middleware (xref:Microsoft.AspNetCore.Builder.StaticFileExtensions.UseStaticFiles%2A) is useful in the following situations that MapStaticAssets can't handle:

:::moniker-end

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

Configure Static File Middleware to serve static assets to clients by calling xref:Microsoft.AspNetCore.Builder.StaticFileExtensions.UseStaticFiles%2A in the app's request processing pipeline. For more information, see xref:fundamentals/static-files.

:::moniker-end

In releases prior to .NET 8, Blazor framework static files, such as the Blazor script, are served via Static File Middleware. In .NET 8 or later, Blazor framework static files are mapped using endpoint routing, and Static File Middleware is no longer used.

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

Static Web Asset Project Mode

This section applies to the .Client project of a Blazor Web App.

The required <StaticWebAssetProjectMode>Default</StaticWebAssetProjectMode> setting in the .Client project of a Blazor Web App reverts Blazor WebAssembly static asset behaviors back to the defaults, so that the project behaves as part of the hosted project. The Blazor WebAssembly SDK (Microsoft.NET.Sdk.BlazorWebAssembly) configures static web assets in a specific way to work in "standalone" mode with a server simply consuming the outputs from the library. This isn't appropriate for a Blazor Web App, where the WebAssembly portion of the app is a logical part of the host and must behave more like a library. For example, the project doesn't expose the styles bundle (for example, BlazorSample.Client.styles.css) and instead only provides the host with the project bundle, so that the host can include it in its own styles bundle.

Changing the value (Default) of <StaticWebAssetProjectMode> or removing the property from the .Client project is not supported.

:::moniker-end

Static files in non-Development environments

This section applies to server-side static files.

When running an app locally, static web assets are only enabled by default in the xref:Microsoft.Extensions.Hosting.Environments.Development environment. To enable static files for environments other than xref:Microsoft.Extensions.Hosting.Environments.Development during local development and testing (for example, xref:Microsoft.Extensions.Hosting.Environments.Staging), call xref:Microsoft.AspNetCore.Hosting.WebHostBuilderExtensions.UseStaticWebAssets%2A on the xref:Microsoft.AspNetCore.Builder.WebApplicationBuilder in the Program file.

Warning

Call xref:Microsoft.AspNetCore.Hosting.WebHostBuilderExtensions.UseStaticWebAssets%2A for the exact environment to prevent activating the feature in production, as it serves files from separate locations on disk other than from the project if called in a production environment. The example in this section checks for the xref:Microsoft.Extensions.Hosting.Environments.Staging environment by calling xref:Microsoft.Extensions.Hosting.HostEnvironmentEnvExtensions.IsStaging%2A.

if (builder.Environment.IsStaging())
{
    builder.WebHost.UseStaticWebAssets();
}

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

Prefix for Blazor WebAssembly assets

This section applies to Blazor Web Apps.

Use the xref:Microsoft.AspNetCore.Components.WebAssembly.Server.WebAssemblyComponentsEndpointOptions.PathPrefix?displayProperty=nameWithType endpoint option to set the path string that indicates the prefix for Blazor WebAssembly assets. The path must correspond to a referenced Blazor WebAssembly application project.

endpoints.MapRazorComponents<App>()
    .AddInteractiveWebAssemblyRenderMode(options => 
        options.PathPrefix = "{PATH PREFIX}");

In the preceding example, the {PATH PREFIX} placeholder is the path prefix and must start with a forward slash (/).

In the following example, the path prefix is set to /path-prefix:

endpoints.MapRazorComponents<App>()
    .AddInteractiveWebAssemblyRenderMode(options => 
        options.PathPrefix = "/path-prefix");

:::moniker-end

Static web asset base path

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

This section applies to standalone Blazor WebAssembly apps.

By default, publishing the app places the app's static assets, including Blazor framework files (_framework folder assets), at the root path (/) in published output. The <StaticWebAssetBasePath> property specified in the project file (.csproj) sets the base path to a non-root path:

<PropertyGroup>
  <StaticWebAssetBasePath>{PATH}</StaticWebAssetBasePath>
</PropertyGroup>

In the preceding example, the {PATH} placeholder is the path.

Without setting the <StaticWebAssetBasePath> property, a standalone app is published at /BlazorStandaloneSample/bin/Release/{TFM}/publish/wwwroot/.

In the preceding example, the {TFM} placeholder is the Target Framework Moniker (TFM) (for example, net6.0).

If the <StaticWebAssetBasePath> property in a standalone Blazor WebAssembly app sets the published static asset path to app1, the root path to the app in published output is /app1.

In the standalone Blazor WebAssembly app's project file (.csproj):

<PropertyGroup>
  <StaticWebAssetBasePath>app1</StaticWebAssetBasePath>
</PropertyGroup>

In published output, the path to the standalone Blazor WebAssembly app is /BlazorStandaloneSample/bin/Release/{TFM}/publish/wwwroot/app1/.

In the preceding example, the {TFM} placeholder is the Target Framework Moniker (TFM) (for example, net6.0).

:::moniker-end

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

This section applies to standalone Blazor WebAssembly apps and hosted Blazor WebAssembly solutions.

By default, publishing the app places the app's static assets, including Blazor framework files (_framework folder assets), at the root path (/) in published output. The <StaticWebAssetBasePath> property specified in the project file (.csproj) sets the base path to a non-root path:

<PropertyGroup>
  <StaticWebAssetBasePath>{PATH}</StaticWebAssetBasePath>
</PropertyGroup>

In the preceding example, the {PATH} placeholder is the path.

Without setting the <StaticWebAssetBasePath> property, the client app of a hosted solution or a standalone app is published at the following paths:

  • In the :::no-loc text="Server"::: project of a hosted Blazor WebAssembly solution: /BlazorHostedSample/Server/bin/Release/{TFM}/publish/wwwroot/
  • In a standalone Blazor WebAssembly app: /BlazorStandaloneSample/bin/Release/{TFM}/publish/wwwroot/

If the <StaticWebAssetBasePath> property in the :::no-loc text="Client"::: project of a hosted Blazor WebAssembly app or in a standalone Blazor WebAssembly app sets the published static asset path to app1, the root path to the app in published output is /app1.

In the :::no-loc text="Client"::: app's project file (.csproj) or the standalone Blazor WebAssembly app's project file (.csproj):

<PropertyGroup>
  <StaticWebAssetBasePath>app1</StaticWebAssetBasePath>
</PropertyGroup>

In published output:

  • Path to the client app in the :::no-loc text="Server"::: project of a hosted Blazor WebAssembly solution: /BlazorHostedSample/Server/bin/Release/{TFM}/publish/wwwroot/app1/
  • Path to a standalone Blazor WebAssembly app: /BlazorStandaloneSample/bin/Release/{TFM}/publish/wwwroot/app1/

The <StaticWebAssetBasePath> property is most commonly used to control the paths to published static assets of multiple Blazor WebAssembly apps in a single hosted deployment. For more information, see xref:blazor/host-and-deploy/multiple-hosted-webassembly. The property is also effective in standalone Blazor WebAssembly apps.

In the preceding examples, the {TFM} placeholder is the Target Framework Moniker (TFM) (for example, net6.0).

:::moniker-end

File mappings and static file options

This section applies to server-side static files.

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

To create additional file mappings with a xref:Microsoft.AspNetCore.StaticFiles.FileExtensionContentTypeProvider or configure other xref:Microsoft.AspNetCore.Builder.StaticFileOptions, use one of the following approaches. In the following examples, the {EXTENSION} placeholder is the file extension, and the {CONTENT TYPE} placeholder is the content type. The namespace for the following API is xref:Microsoft.AspNetCore.StaticFiles.

  • Configure options through dependency injection (DI) in the Program file using xref:Microsoft.AspNetCore.Builder.StaticFileOptions:

    var provider = new FileExtensionContentTypeProvider();
provider.Mappings["{EXTENSION}"] = "{CONTENT TYPE}";

builder.Services.Configure<StaticFileOptions>(options =>
{
    options.ContentTypeProvider = provider;
});

app.UseStaticFiles();

  • Pass the xref:Microsoft.AspNetCore.Builder.StaticFileOptions directly to xref:Microsoft.AspNetCore.Builder.StaticFileExtensions.UseStaticFiles%2A in the Program file:

    var provider = new FileExtensionContentTypeProvider();
provider.Mappings["{EXTENSION}"] = "{CONTENT TYPE}";

app.UseStaticFiles(new StaticFileOptions { ContentTypeProvider = provider });

:::moniker-end

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

To create additional file mappings with a xref:Microsoft.AspNetCore.StaticFiles.FileExtensionContentTypeProvider or configure other xref:Microsoft.AspNetCore.Builder.StaticFileOptions, use one of the following approaches. In the following examples, the {EXTENSION} placeholder is the file extension, and the {CONTENT TYPE} placeholder is the content type.

  • Configure options through dependency injection (DI) in the Program file using xref:Microsoft.AspNetCore.Builder.StaticFileOptions:

    using Microsoft.AspNetCore.StaticFiles;

...

var provider = new FileExtensionContentTypeProvider();
provider.Mappings["{EXTENSION}"] = "{CONTENT TYPE}";

builder.Services.Configure<StaticFileOptions>(options =>
{
    options.ContentTypeProvider = provider;
});

    This approach configures the same file provider used to serve the Blazor script. Make sure that your custom configuration doesn't interfere with serving the Blazor script. For example, don't remove the mapping for JavaScript files by configuring the provider with provider.Mappings.Remove(".js").

  • Use two calls to xref:Microsoft.AspNetCore.Builder.StaticFileExtensions.UseStaticFiles%2A in the Program file:

    • Configure the custom file provider in the first call with xref:Microsoft.AspNetCore.Builder.StaticFileOptions.
    • The second middleware serves the Blazor script, which uses the default static files configuration provided by the Blazor framework.
    using Microsoft.AspNetCore.StaticFiles;

...

var provider = new FileExtensionContentTypeProvider();
provider.Mappings["{EXTENSION}"] = "{CONTENT TYPE}";

app.UseStaticFiles(new StaticFileOptions { ContentTypeProvider = provider });
app.UseStaticFiles();

  • You can avoid interfering with serving _framework/blazor.server.js by using xref:Microsoft.AspNetCore.Builder.MapWhenExtensions.MapWhen%2A to execute a custom Static File Middleware:

    app.MapWhen(ctx => !ctx.Request.Path
    .StartsWithSegments("/_framework/blazor.server.js"),
        subApp => subApp.UseStaticFiles(new StaticFileOptions() { ... }));

:::moniker-end

Additional resources

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

App base path

:::moniker-end

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

  • App base path
  • xref:blazor/host-and-deploy/multiple-hosted-webassembly

:::moniker-end