Host and deploy ASP.NET Core Blazor

By Luke Latham, Rainer Stropek, and Daniel Roth

Publish the app

Apps are published for deployment in Release configuration.

  1. Select Build > Publish {APPLICATION} from the navigation bar.
  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.

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/.

To provide configuration for the Blazor app's base path of https://www.contoso.com/CoolApp/, the <base> tag's href attribute is set to the relative root path in the Pages/_Host.cshtml file (Blazor Server) or wwwroot/index.html file (Blazor WebAssembly):

<base href="/CoolApp/">

Blazor Server apps additionally set the server-side base path by calling UsePathBase in the app's request pipeline of Startup.Configure:

app.UsePathBase("/CoolApp");

By providing the relative URL path, 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 cases, the app's relative URL base path is a forward slash (<base href="/" />), which is the default configuration for a Blazor app. 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.

To set the app's base path, update the <base> tag within the <head> tag elements of the Pages/_Host.cshtml file (Blazor Server) or wwwroot/index.html file (Blazor WebAssembly). Set the href attribute value to /{RELATIVE URL PATH}/ (the trailing slash is required), where {RELATIVE URL PATH} is the app's full relative URL path.

For an 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

The Blazor WebAssembly app responds locally at http://localhost:port/CoolApp.

Deployment

For deployment guidance, see the following topics: