Host and deploy ASP.NET Core Blazor

This article explains how to host and deploy Blazor apps.

Publish the app

Apps are published for deployment in Release configuration.

Note

Publish a hosted Blazor WebAssembly solution from the Server project.

  1. Select the Publish {APPLICATION} command from the Build menu, where the {APPLICATION} placeholder the app's name.
  2. Select the publish target. To publish locally, select Folder.
  3. Accept the default location in the Choose a folder field or specify a different location. Select the Publish button.

Publishing the app triggers a restore of the project's dependencies and builds the project before creating the assets for deployment. As part of the build process, unused methods and assemblies are removed to reduce app download size and load times.

Publish locations:

  • Blazor WebAssembly
    • Standalone: The app is published into the /bin/Release/{TARGET FRAMEWORK}/publish/wwwroot folder. To deploy the app as a static site, copy the contents of the wwwroot folder to the static site host.
    • Hosted: The client Blazor WebAssembly app is published into the /bin/Release/{TARGET FRAMEWORK}/publish/wwwroot folder of the server app, along with any other static web assets of the server app. Deploy the contents of the publish folder to the host.
  • Blazor Server: The app is published into the /bin/Release/{TARGET FRAMEWORK}/publish folder. Deploy the contents of the publish folder to the host.

The assets in the folder are deployed to the web server. Deployment might be a manual or automated process depending on the development tools in use.

IIS

To host a Blazor app in IIS, see the following resources:

  • IIS hosting
  • Host and deploy ASP.NET Core Blazor Server: Blazor Server apps running on IIS, including IIS with Azure Virtual Machines (VMs) running Windows OS and Azure App Service.
  • Host and deploy ASP.NET Core Blazor WebAssembly: Includes additional guidance for Blazor WebAssembly apps hosted on IIS, including static site hosting, custom web.config files, URL rewriting, sub-apps, compression, and Azure Storage static file hosting.
  • IIS sub-application hosting
    • Follow the guidance in the App base path section for the Blazor app prior to publishing the app. The examples use an app base path of /CoolApp.
    • Follow the sub-application configuration guidance in Advanced configuration. The sub-app's folder path under the root site becomes the virtual path of the sub-app. For an app base path of /CoolApp, the Blazor app is placed in a folder named CoolApp under the root site and the sub-app takes on a virtual path of /CoolApp.

Sharing an app pool among ASP.NET Core apps isn't supported, including for Blazor apps. Use one app pool per app when hosting with IIS, and avoid the use of IIS's virtual directories for hosting multiple apps.

One or more Blazor WebAssembly apps hosted by an ASP.NET Core app, known as a hosted Blazor WebAssembly solution, are supported for one app pool. However, we don't recommend or support assigning a single app pool to multiple hosted Blazor WebAssembly solutions or in sub-app hosting scenarios.

For more information on solutions, see Tooling for ASP.NET Core Blazor.

App base path

The app base path is the app's root URL path. Consider the following ASP.NET Core app and Blazor sub-app:

  • The ASP.NET Core app is named MyApp:
    • The app physically resides at d:/MyApp.
    • Requests are received at https://www.contoso.com/{MYAPP RESOURCE}.
  • A Blazor app named CoolApp is a sub-app of MyApp:
    • The sub-app physically resides at d:/MyApp/CoolApp.
    • Requests are received at https://www.contoso.com/CoolApp/{COOLAPP RESOURCE}.

Without specifying additional configuration for CoolApp, the sub-app in this scenario has no knowledge of where it resides on the server. For example, the app can't construct correct relative URLs to its resources without knowing that it resides at the relative URL path /CoolApp/. This scenario also applies in various hosting and reverse proxy scenarios when an app isn't hosted at a root URL path.

To provide configuration for the Blazor app's base path of https://www.contoso.com/CoolApp/, set the relative root path.

By configuring the relative URL path for an app, a component that isn't in the root directory can construct URLs relative to the app's root path. Components at different levels of the directory structure can build links to other resources at locations throughout the app. The app base path is also used to intercept selected hyperlinks where the href target of the link is within the app base path URI space. The Blazor router handles the internal navigation.

In many hosting scenarios, the relative URL path to the app is the root of the app. In these default cases, the app's relative URL base path is the following:

  • Blazor WebAssembly: / configured as <base href="/" />.
  • Blazor Server: ~/ configured as <base href="~/" />.

For the location of <head> content in Blazor apps, see ASP.NET Core Blazor project structure.

In other hosting scenarios, such as GitHub Pages and IIS sub-apps, the app base path must be set to the server's relative URL path of the app.

  • Standalone Blazor WebAssembly:

    wwwroot/index.html:

    <base href="/CoolApp/">
    

    The trailing slash is required.

  • Hosted Blazor WebAssembly:

    In the Client project, wwwroot/index.html:

    <base href="/CoolApp/">
    

    The trailing slash is required.

    In the Server project, call UsePathBase first in the app's request processing pipeline (Program.cs) immediately after the WebApplicationBuilder is built (builder.Build()) to configure the base path for any following middleware that interacts with the request path:

    app.UsePathBase("/CoolApp");
    
  • In a Blazor Server app, use either of the following approaches:

    • Option 1: Use the <base> tag to set the app's base path (location of <head> content):

      <base href="/CoolApp/">
      

      The trailing slash is required.

    • Option 2: Call UsePathBase first in the app's request processing pipeline (Program.cs) immediately after the WebApplicationBuilder is built (builder.Build()) to configure the base path for any following middleware that interacts with the request path:

      app.UsePathBase("/CoolApp");
      

      Calling UsePathBase is recommended when you also wish to run the Blazor Server app locally. For example, supply the launch URL in Properties/launchSettings.json:

      "launchUrl": "https://localhost:{PORT}/CoolApp",
      

      The {PORT} placeholder in the preceding example is the port that matches the secure port in the applicationUrl configuration path. The following example shows the full launch profile for an app at port 7279:

      "BlazorSample": {
        "commandName": "Project",
        "dotnetRunMessages": true,
        "launchBrowser": true,
        "applicationUrl": "https://localhost:7279;http://localhost:5279",
        "launchUrl": "https://localhost:7279/CoolApp",
        "environmentVariables": {
          "ASPNETCORE_ENVIRONMENT": "Development"
      }
      

      For more information on the launchSettings.json file, see Use multiple environments in ASP.NET Core. For additional information on Blazor app base paths and hosting, see <base href="/" /> or base-tag alternative for Blazor MVC integration (dotnet/aspnetcore #43191).

Note

When using WebApplication (see Migrate from ASP.NET Core 5.0 to 6.0), app.UseRouting must be called after UsePathBase so that the routing middleware can observe the modified path before matching routes. Otherwise, routes are matched before the path is rewritten by UsePathBase as described in the Middleware Ordering and Routing articles.

Do not prefix links throughout the app with a forward slash. Either avoid the use of a path segment separator or use dot-slash (./) relative path notation:

  • ❌ Incorrect: <a href="/account">
  • ✔️ Correct: <a href="account">
  • ✔️ Correct: <a href="./account">

In Blazor WebAssembly web API requests with the HttpClient service, confirm that JSON helpers (HttpClientJsonExtensions) do not prefix URLs with a forward slash (/):

  • ❌ Incorrect: var rsp = await client.GetFromJsonAsync("/api/Account");
  • ✔️ Correct: var rsp = await client.GetFromJsonAsync("api/Account");

Do not prefix Navigation Manager relative links with a forward slash. Either avoid the use of a path segment separator or use dot-slash (./) relative path notation:

  • ❌ Incorrect: NavigationManager.NavigateTo("/other");
  • ✔️ Correct: NavigationManager.NavigateTo("other");
  • ✔️ Correct: NavigationManager.NavigateTo("./other");

In typical configurations for Azure/IIS hosting, additional configuration usually isn't required. In some non-IIS hosting and reverse proxy hosting scenarios, additional Static File Middleware configuration might be required to serve static files correctly (for example, app.UseStaticFiles("/CoolApp");). The required configuration might require further configuration to serve the Blazor script (_framework/blazor.server.js or _framework/blazor.webassembly.js). For more information, see ASP.NET Core Blazor static files.

For a Blazor WebAssembly app with a non-root relative URL path (for example, <base href="/CoolApp/">), the app fails to find its resources when run locally. To overcome this problem during local development and testing, you can supply a path base argument that matches the href value of the <base> tag at runtime. Don't include a trailing slash. To pass the path base argument when running the app locally, execute the dotnet run command from the app's directory with the --pathbase option:

dotnet run --pathbase=/{RELATIVE URL PATH (no trailing slash)}

For a Blazor WebAssembly app with a relative URL path of /CoolApp/ (<base href="/CoolApp/">), the command is:

dotnet run --pathbase=/CoolApp

If you prefer to configure the app's launch profile to specify the pathbase automatically instead of manually with dotnet run, set the commandLineArgs property in Properties/launchSettings.json. The following also configures the launch URL (launchUrl):

"commandLineArgs": "--pathbase=/{RELATIVE URL PATH (no trailing slash)}",
"launchUrl": "{RELATIVE URL PATH (no trailing slash)}",

Using CoolApp as the example:

"commandLineArgs": "--pathbase=/CoolApp",
"launchUrl": "CoolApp",

Using either dotnet run with the --pathbase option or a launch profile configuration that sets the base path, the Blazor WebAssembly app responds locally at http://localhost:port/CoolApp.

For more information on the launchSettings.json file, see Use multiple environments in ASP.NET Core. For additional information on Blazor app base paths and hosting, see <base href="/" /> or base-tag alternative for Blazor MVC integration (dotnet/aspnetcore #43191).

Blazor Server MapFallbackToPage configuration

In scenarios where an app requires a separate area with custom resources and Razor components:

  • Create a folder within the app's Pages folder to hold the resources. For example, an administrator section of an app is created in a new folder named Admin (Pages/Admin).

  • Create a root page (_Host.cshtml) for the area. For example, create a Pages/Admin/_Host.cshtml file from the app's main root page (Pages/_Host.cshtml). Don't provide an @page directive in the Admin _Host page.

  • Add a layout to the area's folder (for example, Pages/Admin/_Layout.razor). In the layout for the separate area, set the <base> tag href to match the area's folder (for example, <base href="/Admin/" />). For demonstration purposes, add ~/ to the static resources in the page. For example:

    • ~/css/bootstrap/bootstrap.min.css
    • ~/css/site.css
    • ~/BlazorSample.styles.css (the example app's namespace is BlazorSample)
    • ~/_framework/blazor.server.js (Blazor script)
  • If the area should have its own static asset folder, add the folder and specify its location to Static File Middleware in Program.cs (for example, app.UseStaticFiles("/Admin/wwwroot")).

  • Razor components are added to the area's folder. At a minimum, add an Index component to the area folder with the correct @page directive for the area. For example, add a Pages/Admin/Index.razor file based on the app's default Pages/Index.razor file. Indicate the Admin area as the route template at the top of the file (@page "/admin"). Add additional components as needed. For example, Pages/Admin/Component1.razor with an @page directive and route template of @page "/admin/component1.

  • In Program.cs, call MapFallbackToPage for the area's request path immediately before the fallback root page path to the _Host page:

    ...
    app.UseRouting();
    
    app.MapBlazorHub();
    app.MapFallbackToPage("~/Admin/{*clientroutes:nonfile}", "/Admin/_Host");
    app.MapFallbackToPage("/_Host");
    
    app.Run();
    

Host multiple Blazor WebAssembly apps

For more information on hosting multiple Blazor WebAssembly apps in a hosted Blazor solution, see Multiple hosted ASP.NET Core Blazor WebAssembly apps.

Deployment

For deployment guidance, see the following topics:

Publish the app

Apps are published for deployment in Release configuration.

  1. Select the Publish {APPLICATION} command from the Build menu, where the {APPLICATION} placeholder the app's name.
  2. Select the publish target. To publish locally, select Folder.
  3. Accept the default location in the Choose a folder field or specify a different location. Select the Publish button.

Publishing the app triggers a restore of the project's dependencies and builds the project before creating the assets for deployment. As part of the build process, unused methods and assemblies are removed to reduce app download size and load times.

Publish locations:

  • Blazor WebAssembly
    • Standalone: The app is published into the /bin/Release/{TARGET FRAMEWORK}/publish/wwwroot folder. To deploy the app as a static site, copy the contents of the wwwroot folder to the static site host.
    • Hosted: The client Blazor WebAssembly app is published into the /bin/Release/{TARGET FRAMEWORK}/publish/wwwroot folder of the server app, along with any other static web assets of the server app. Deploy the contents of the publish folder to the host.
  • Blazor Server: The app is published into the /bin/Release/{TARGET FRAMEWORK}/publish folder. Deploy the contents of the publish folder to the host.

The assets in the folder are deployed to the web server. Deployment might be a manual or automated process depending on the development tools in use.

IIS

To host a Blazor app in IIS, see the following resources:

  • IIS hosting
  • Host and deploy ASP.NET Core Blazor Server: Blazor Server apps running on IIS, including IIS with Azure Virtual Machines (VMs) running Windows OS and Azure App Service.
  • Host and deploy ASP.NET Core Blazor WebAssembly: Includes additional guidance for Blazor WebAssembly apps hosted on IIS, including static site hosting, custom web.config files, URL rewriting, sub-apps, compression, and Azure Storage static file hosting.
  • IIS sub-application hosting
    • Follow the guidance in the App base path section for the Blazor app prior to publishing the app. The examples use an app base path of /CoolApp.
    • Follow the sub-application configuration guidance in Advanced configuration. The sub-app's folder path under the root site becomes the virtual path of the sub-app. For an app base path of /CoolApp, the Blazor app is placed in a folder named CoolApp under the root site and the sub-app takes on a virtual path of /CoolApp.

Sharing an app pool among ASP.NET Core apps isn't supported, including for Blazor apps. Use one app pool per app when hosting with IIS, and avoid the use of IIS's virtual directories for hosting multiple apps.

One or more Blazor WebAssembly apps hosted by an ASP.NET Core app, known as a hosted Blazor WebAssembly solution, are supported for one app pool. However, we don't recommend or support assigning a single app pool to multiple hosted Blazor WebAssembly solutions or in sub-app hosting scenarios.

For more information on solutions, see Tooling for ASP.NET Core Blazor.

App base path

The app base path is the app's root URL path. Consider the following ASP.NET Core app and Blazor sub-app:

  • The ASP.NET Core app is named MyApp:
    • The app physically resides at d:/MyApp.
    • Requests are received at https://www.contoso.com/{MYAPP RESOURCE}.
  • A Blazor app named CoolApp is a sub-app of MyApp:
    • The sub-app physically resides at d:/MyApp/CoolApp.
    • Requests are received at https://www.contoso.com/CoolApp/{COOLAPP RESOURCE}.

Without specifying additional configuration for CoolApp, the sub-app in this scenario has no knowledge of where it resides on the server. For example, the app can't construct correct relative URLs to its resources without knowing that it resides at the relative URL path /CoolApp/. This scenario also applies in various hosting and reverse proxy scenarios when an app isn't hosted at a root URL path.

To provide configuration for the Blazor app's base path of https://www.contoso.com/CoolApp/, set the relative root path.

By configuring the relative URL path for an app, a component that isn't in the root directory can construct URLs relative to the app's root path. Components at different levels of the directory structure can build links to other resources at locations throughout the app. The app base path is also used to intercept selected hyperlinks where the href target of the link is within the app base path URI space. The Blazor router handles the internal navigation.

In many hosting scenarios, the relative URL path to the app is the root of the app. In these default cases, the app's relative URL base path is the following:

  • Blazor WebAssembly: / configured as <base href="/" /> in wwwroot/index.html.
  • Blazor Server: ~/ configured as <base href="~/" /> in Pages/_Host.cshtml.

In other hosting scenarios, such as GitHub Pages and IIS sub-apps, the app base path must be set to the server's relative URL path of the app.

  • Standalone Blazor WebAssembly:

    wwwroot/index.html:

    <base href="/CoolApp/">
    

    The trailing slash is required.

  • Hosted Blazor WebAssembly:

    In the Client project, wwwroot/index.html:

    <base href="/CoolApp/">
    

    The trailing slash is required.

    In the Server project, call UsePathBase first in the app's request processing pipeline (the Configure method of Startup.cs) to configure the base path for any following middleware that interacts with the request path:

    app.UsePathBase("/CoolApp");
    
  • In a Blazor Server app, use either of the following approaches:

    • Option 1: Use the <base> tag in Pages/_Host.cshtml to set the app's base path:

      <base href="/CoolApp/">
      

      The trailing slash is required.

    • Option 2: Call UsePathBase first in the app's request processing pipeline (the Configure method of Startup.cs) to configure the base path for any following middleware that interacts with the request path:

      app.UsePathBase("/CoolApp");
      

      Calling UsePathBase is recommended when you also wish to run the Blazor Server app locally. For example, supply the launch URL in Properties/launchSettings.json:

      "launchUrl": "https://localhost:{PORT}/CoolApp",
      

      The {PORT} placeholder in the preceding example is the port that matches the secure port in the applicationUrl configuration path. The following example shows the full launch profile for an app at port 7279:

      "BlazorSample": {
        "commandName": "Project",
        "dotnetRunMessages": true,
        "launchBrowser": true,
        "applicationUrl": "https://localhost:7279;http://localhost:5279",
        "launchUrl": "https://localhost:7279/CoolApp",
        "environmentVariables": {
          "ASPNETCORE_ENVIRONMENT": "Development"
      }
      

      For more information on the launchSettings.json file, see Use multiple environments in ASP.NET Core. For additional information on Blazor app base paths and hosting, see <base href="/" /> or base-tag alternative for Blazor MVC integration (dotnet/aspnetcore #43191).

For a Blazor WebAssembly app with a non-root relative URL path (for example, <base href="/CoolApp/">), the app fails to find its resources when run locally. To overcome this problem during local development and testing, you can supply a path base argument that matches the href value of the <base> tag at runtime. Don't include a trailing slash. To pass the path base argument when running the app locally, execute the dotnet run command from the app's directory with the --pathbase option:

dotnet run --pathbase=/{RELATIVE URL PATH (no trailing slash)}

For a Blazor WebAssembly app with a relative URL path of /CoolApp/ (<base href="/CoolApp/">), the command is:

dotnet run --pathbase=/CoolApp

If you prefer to configure the app's launch profile to specify the pathbase automatically instead of manually with dotnet run, set the commandLineArgs property in Properties/launchSettings.json. The following also configures the launch URL (launchUrl):

"commandLineArgs": "--pathbase=/{RELATIVE URL PATH (no trailing slash)}",
"launchUrl": "{RELATIVE URL PATH (no trailing slash)}",

Using CoolApp as the example:

"commandLineArgs": "--pathbase=/CoolApp",
"launchUrl": "CoolApp",

Using either dotnet run with the --pathbase option or a launch profile configuration that sets the base path, the Blazor WebAssembly app responds locally at http://localhost:port/CoolApp.

For more information on the launchSettings.json file, see Use multiple environments in ASP.NET Core. For additional information on Blazor app base paths and hosting, see <base href="/" /> or base-tag alternative for Blazor MVC integration (dotnet/aspnetcore #43191).

For additional third-party host support:

Blazor Server MapFallbackToPage configuration

In scenarios where an app requires a separate area with custom resources and Razor components:

  • Create a folder within the app's Pages folder to hold the resources. For example, an administrator section of an app is created in a new folder named Admin (Pages/Admin).

  • Create a root page (_Host.cshtml) for the area. For example, create a Pages/Admin/_Host.cshtml file from the app's main root page (Pages/_Host.cshtml). Don't provide an @page directive in the Admin _Host page.

  • Add a layout to the area's folder (for example, Pages/Admin/_Layout.razor). In the layout for the separate area, set the <base> tag href to match the area's folder (for example, <base href="/Admin/" />). For demonstration purposes, add ~/ to the static resources in the page. For example:

    • ~/css/bootstrap/bootstrap.min.css
    • ~/css/site.css
    • ~/BlazorSample.styles.css (the example app's namespace is BlazorSample)
    • ~/_framework/blazor.server.js (Blazor script)
  • If the area should have its own static asset folder, add the folder and specify its location to Static File Middleware in Program.cs (for example, app.UseStaticFiles("/Admin/wwwroot")).

  • Razor components are added to the area's folder. At a minimum, add an Index component to the area folder with the correct @page directive for the area. For example, add a Pages/Admin/Index.razor file based on the app's default Pages/Index.razor file. Indicate the Admin area as the route template at the top of the file (@page "/admin"). Add additional components as needed. For example, Pages/Admin/Component1.razor with an @page directive and route template of @page "/admin/component1.

  • In Startup.Configure, call MapFallbackToPage for the area's request path immediately before the fallback root page path to the _Host page:

    ...
    app.UseRouting();
    
    app.MapBlazorHub();
    app.MapFallbackToPage("~/Admin/{*clientroutes:nonfile}", "/Admin/_Host");
    app.MapFallbackToPage("/_Host");
    
    app.Run();
    

Host multiple Blazor WebAssembly apps

For more information on hosting multiple Blazor WebAssembly apps in a hosted Blazor solution, see Multiple hosted ASP.NET Core Blazor WebAssembly apps.

Deployment

For deployment guidance, see the following topics:

Publish the app

Apps are published for deployment in Release configuration.

  1. Select the Publish {APPLICATION} command from the Build menu, where the {APPLICATION} placeholder the app's name.
  2. Select the publish target. To publish locally, select Folder.
  3. Accept the default location in the Choose a folder field or specify a different location. Select the Publish button.

Publishing the app triggers a restore of the project's dependencies and builds the project before creating the assets for deployment. As part of the build process, unused methods and assemblies are removed to reduce app download size and load times.

Publish locations:

  • Blazor WebAssembly
    • Standalone: The app is published into the /bin/Release/{TARGET FRAMEWORK}/publish/wwwroot folder. To deploy the app as a static site, copy the contents of the wwwroot folder to the static site host.
    • Hosted: The client Blazor WebAssembly app is published into the /bin/Release/{TARGET FRAMEWORK}/publish/wwwroot folder of the server app, along with any other static web assets of the server app. Deploy the contents of the publish folder to the host.
  • Blazor Server: The app is published into the /bin/Release/{TARGET FRAMEWORK}/publish folder. Deploy the contents of the publish folder to the host.

The assets in the folder are deployed to the web server. Deployment might be a manual or automated process depending on the development tools in use.

IIS

To host a Blazor app in IIS, see the following resources:

  • IIS hosting
  • Host and deploy ASP.NET Core Blazor Server: Blazor Server apps running on IIS, including IIS with Azure Virtual Machines (VMs) running Windows OS and Azure App Service.
  • Host and deploy ASP.NET Core Blazor WebAssembly: Includes additional guidance for Blazor WebAssembly apps hosted on IIS, including static site hosting, custom web.config files, URL rewriting, sub-apps, compression, and Azure Storage static file hosting.
  • IIS sub-application hosting
    • Follow the guidance in the App base path section for the Blazor app prior to publishing the app. The examples use an app base path of /CoolApp.
    • Follow the sub-application configuration guidance in Advanced configuration. The sub-app's folder path under the root site becomes the virtual path of the sub-app. For an app base path of /CoolApp, the Blazor app is placed in a folder named CoolApp under the root site and the sub-app takes on a virtual path of /CoolApp.

Sharing an app pool among ASP.NET Core apps isn't supported, including for Blazor apps. Use one app pool per app when hosting with IIS, and avoid the use of IIS's virtual directories for hosting multiple apps.

One or more Blazor WebAssembly apps hosted by an ASP.NET Core app, known as a hosted Blazor WebAssembly solution, are supported for one app pool. However, we don't recommend or support assigning a single app pool to multiple hosted Blazor WebAssembly solutions or in sub-app hosting scenarios.

For more information on solutions, see Tooling for ASP.NET Core Blazor.

App base path

The app base path is the app's root URL path. Consider the following ASP.NET Core app and Blazor sub-app:

  • The ASP.NET Core app is named MyApp:
    • The app physically resides at d:/MyApp.
    • Requests are received at https://www.contoso.com/{MYAPP RESOURCE}.
  • A Blazor app named CoolApp is a sub-app of MyApp:
    • The sub-app physically resides at d:/MyApp/CoolApp.
    • Requests are received at https://www.contoso.com/CoolApp/{COOLAPP RESOURCE}.

Without specifying additional configuration for CoolApp, the sub-app in this scenario has no knowledge of where it resides on the server. For example, the app can't construct correct relative URLs to its resources without knowing that it resides at the relative URL path /CoolApp/. This scenario also applies in various hosting and reverse proxy scenarios when an app isn't hosted at a root URL path.

To provide configuration for the Blazor app's base path of https://www.contoso.com/CoolApp/, set the relative root path.

By configuring the relative URL path for an app, a component that isn't in the root directory can construct URLs relative to the app's root path. Components at different levels of the directory structure can build links to other resources at locations throughout the app. The app base path is also used to intercept selected hyperlinks where the href target of the link is within the app base path URI space. The Blazor router handles the internal navigation.

In many hosting scenarios, the relative URL path to the app is the root of the app. In these default cases, the app's relative URL base path is the following:

  • Blazor WebAssembly: / configured as <base href="/" /> in wwwroot/index.html.
  • Blazor Server: ~/ configured as <base href="~/" /> in Pages/_Host.cshtml.

In other hosting scenarios, such as GitHub Pages and IIS sub-apps, the app base path must be set to the server's relative URL path of the app.

  • Standalone Blazor WebAssembly:

    wwwroot/index.html:

    <base href="/CoolApp/">
    

    The trailing slash is required.

  • Hosted Blazor WebAssembly:

    In the Client project, wwwroot/index.html:

    <base href="/CoolApp/">
    

    The trailing slash is required.

    In the Server project, call UsePathBase first in the app's request processing pipeline (the Configure method of Startup.cs) to configure the base path for any following middleware that interacts with the request path:

    app.UsePathBase("/CoolApp");
    
  • In a Blazor Server app, use either of the following approaches:

    • Option 1: Use the <base> tag in Pages/_Host.cshtml to set the app's base path:

      <base href="/CoolApp/">
      

      The trailing slash is required.

    • Option 2: Call UsePathBase first in the app's request processing pipeline (the Configure method of Startup.cs) to configure the base path for any following middleware that interacts with the request path:

      app.UsePathBase("/CoolApp");
      

      Calling UsePathBase is recommended when you also wish to run the Blazor Server app locally. For example, supply the launch URL in Properties/launchSettings.json:

      "launchUrl": "https://localhost:{PORT}/CoolApp",
      

      The {PORT} placeholder in the preceding example is the port that matches the secure port in the applicationUrl configuration path. The following example shows the full launch profile for an app at port 7279:

      "BlazorSample": {
        "commandName": "Project",
        "dotnetRunMessages": true,
        "launchBrowser": true,
        "applicationUrl": "https://localhost:7279;http://localhost:5279",
        "launchUrl": "https://localhost:7279/CoolApp",
        "environmentVariables": {
          "ASPNETCORE_ENVIRONMENT": "Development"
      }
      

      For more information on the launchSettings.json file, see Use multiple environments in ASP.NET Core. For additional information on Blazor app base paths and hosting, see <base href="/" /> or base-tag alternative for Blazor MVC integration (dotnet/aspnetcore #43191).

For a Blazor WebAssembly app with a non-root relative URL path (for example, <base href="/CoolApp/">), the app fails to find its resources when run locally. To overcome this problem during local development and testing, you can supply a path base argument that matches the href value of the <base> tag at runtime. Don't include a trailing slash. To pass the path base argument when running the app locally, execute the dotnet run command from the app's directory with the --pathbase option:

dotnet run --pathbase=/{RELATIVE URL PATH (no trailing slash)}

For a Blazor WebAssembly app with a relative URL path of /CoolApp/ (<base href="/CoolApp/">), the command is:

dotnet run --pathbase=/CoolApp

If you prefer to configure the app's launch profile to specify the pathbase automatically instead of manually with dotnet run, set the commandLineArgs property in Properties/launchSettings.json. The following also configures the launch URL (launchUrl):

"commandLineArgs": "--pathbase=/{RELATIVE URL PATH (no trailing slash)}",
"launchUrl": "{RELATIVE URL PATH (no trailing slash)}",

Using CoolApp as the example:

"commandLineArgs": "--pathbase=/CoolApp",
"launchUrl": "CoolApp",

Using either dotnet run with the --pathbase option or a launch profile configuration that sets the base path, the Blazor WebAssembly app responds locally at http://localhost:port/CoolApp.

For more information on the launchSettings.json file, see Use multiple environments in ASP.NET Core. For additional information on Blazor app base paths and hosting, see <base href="/" /> or base-tag alternative for Blazor MVC integration (dotnet/aspnetcore #43191).

For additional third-party host support:

Blazor Server MapFallbackToPage configuration

In scenarios where an app requires a separate area with custom resources and Razor components:

  • Create a folder within the app's Pages folder to hold the resources. For example, an administrator section of an app is created in a new folder named Admin (Pages/Admin).

  • Create a root page (_Host.cshtml) for the area. For example, create a Pages/Admin/_Host.cshtml file from the app's main root page (Pages/_Host.cshtml). Don't provide an @page directive in the Admin _Host page.

  • Add a layout to the area's folder (for example, Pages/Admin/_Layout.razor). In the layout for the separate area, set the <base> tag href to match the area's folder (for example, <base href="/Admin/" />). For demonstration purposes, add ~/ to the static resources in the page. For example:

    • ~/css/bootstrap/bootstrap.min.css
    • ~/css/site.css
    • ~/BlazorSample.styles.css (the example app's namespace is BlazorSample)
    • ~/_framework/blazor.server.js (Blazor script)
  • If the area should have its own static asset folder, add the folder and specify its location to Static File Middleware in Program.cs (for example, app.UseStaticFiles("/Admin/wwwroot")).

  • Razor components are added to the area's folder. At a minimum, add an Index component to the area folder with the correct @page directive for the area. For example, add a Pages/Admin/Index.razor file based on the app's default Pages/Index.razor file. Indicate the Admin area as the route template at the top of the file (@page "/admin"). Add additional components as needed. For example, Pages/Admin/Component1.razor with an @page directive and route template of @page "/admin/component1.

  • In Startup.Configure.cs, call MapFallbackToPage for the area's request path immediately before the fallback root page path to the _Host page:

    ...
    app.UseRouting();
    
    app.MapBlazorHub();
    app.MapFallbackToPage("~/Admin/{*clientroutes:nonfile}", "/Admin/_Host");
    app.MapFallbackToPage("/_Host");
    
    app.Run();
    

Host multiple Blazor WebAssembly apps

For more information on hosting multiple Blazor WebAssembly apps in a hosted Blazor solution, see Multiple hosted ASP.NET Core Blazor WebAssembly apps.

Deployment

For deployment guidance, see the following topics: