[Azure App Service](https://azure.microsoft.com/services/app-service/) is a [Microsoft cloud computing platform service](https://azure.microsoft.com/) for hosting web apps, including ASP.NET Core.
## Useful resources
The Azure [Web Apps Documentation](/azure/app-service/) is the home for Azure Apps documentation, tutorials, samples, how-to guides, and other resources. Two notable tutorials that pertain to hosting ASP.NET Core apps are:
[Quickstart: Create an ASP.NET Core web app in Azure](/azure/app-service/app-service-web-get-started-dotnet)
Use Visual Studio to create and deploy an ASP.NET Core web app to Azure App Service on Windows.
[Quickstart: Create a .NET Core web app in App Service on Linux](/azure/app-service/containers/quickstart-dotnetcore)
Use the command line to create and deploy an ASP.NET Core web app to Azure App Service on Linux.
The following articles are available in ASP.NET Core documentation:
* [Microsoft.AspNetCore.AzureAppServices.HostingStartup](https://www.nuget.org/packages/Microsoft.AspNetCore.AzureAppServices.HostingStartup/) uses [IHostingStartup](xref:fundamentals/configuration/platform-specific-configuration) to provide ASP.NET Core light-up integration with Azure App Service. The added logging features are provided by the `Microsoft.AspNetCore.AzureAppServicesIntegration` package.
* [Microsoft.AspNetCore.AzureAppServicesIntegration](https://www.nuget.org/packages/Microsoft.AspNetCore.AzureAppServicesIntegration/) executes [AddAzureWebAppDiagnostics](/dotnet/api/microsoft.extensions.logging.azureappservicesloggerfactoryextensions.addazurewebappdiagnostics) to add Azure App Service diagnostics logging providers in the `Microsoft.Extensions.Logging.AzureAppServices` package.
* [Microsoft.Extensions.Logging.AzureAppServices](https://www.nuget.org/packages/Microsoft.Extensions.Logging.AzureAppServices/) provides logger implementations to support Azure App Service diagnostics logs and log streaming features.
If targeting .NET Core and referencing the [Microsoft.AspNetCore.All metapackage](xref:fundamentals/metapackage), the packages are already included. The packages are absent from the newer [Microsoft.AspNetCore.App metapackage](xref:fundamentals/metapackage-app). If targeting .NET Framework or referencing the `Microsoft.AspNetCore.App` metapackage, reference the individual logging packages.
## Override app configuration using the Azure Portal
The **App Settings** area of the **Application settings** blade permits you to set environment variables for the app. Environment variables can be consumed by the [Environment Variables Configuration Provider](xref:fundamentals/configuration/index#environment-variables-configuration-provider).
When an app uses the [Web Host](xref:fundamentals/host/web-host) and builds the host using [WebHost.CreateDefaultBuilder](/dotnet/api/microsoft.aspnetcore.webhost.createdefaultbuilder), environment variables that configure the host use the `ASPNETCORE_` prefix. For more information, see <xref:fundamentals/host/web-host> and the [Environment Variables Configuration Provider](xref:fundamentals/configuration/index#environment-variables-configuration-provider).
When an app uses the [Generic Host](xref:fundamentals/host/generic-host), environment variables aren't loaded into an app's configuration by default and the configuration provider must be added by the developer. The developer determines the environment variable prefix when the configuration provider is added. For more information, see <xref:fundamentals/host/generic-host> and the [Environment Variables Configuration Provider](xref:fundamentals/configuration/index#environment-variables-configuration-provider).
The IIS Integration Middleware, which configures Forwarded Headers Middleware, and the ASP.NET Core Module are configured to forward the scheme (HTTP/HTTPS) and the remote IP address where the request originated. Additional configuration might be required for apps hosted behind additional proxy servers and load balancers. For more information, see [Configure ASP.NET Core to work with proxy servers and load balancers](xref:host-and-deploy/proxy-load-balancer).
[Troubleshoot ASP.NET Core on Azure App Service](xref:host-and-deploy/azure-apps/troubleshoot)
Learn how to diagnose issues with Azure App Service deployments with ASP.NET Core apps.
[Common errors reference for Azure App Service and IIS with ASP.NET Core](xref:host-and-deploy/azure-iis-errors-reference)
See the common deployment configuration errors for apps hosted by Azure App Service/IIS with troubleshooting advice.
## Data Protection key ring and deployment slots
[Data Protection keys](xref:security/data-protection/implementation/key-management#data-protection-implementation-key-management) are persisted to the *%HOME%\ASP.NET\DataProtection-Keys* folder. This folder is backed by network storage and is synchronized across all machines hosting the app. Keys aren't protected at rest. This folder supplies the key ring to all instances of an app in a single deployment slot. Separate deployment slots, such as Staging and Production, don't share a key ring.
When swapping between deployment slots, any system using data protection won't be able to decrypt stored data using the key ring inside the previous slot. ASP.NET Cookie Middleware uses data protection to protect its cookies. This leads to users being signed out of an app that uses the standard ASP.NET Cookie Middleware. For a slot-independent key ring solution, use an external key ring provider, such as:
* Azure Blob Storage
* Azure Key Vault
* SQL store
* Redis cache
For more information, see [Key storage providers](xref:security/data-protection/implementation/key-storage-providers).
1. Select the **ASP.NET Core <x.y> (x86) Runtime** extension from the list, where `<x.y>` is the ASP.NET Core preview version (for example, **ASP.NET Core 2.2 (x86) Runtime**). The x86 runtime is appropriate for [framework-dependent deployments](/dotnet/core/deploying/#framework-dependent-deployments-fdd) that rely on out-of-process hosting by the ASP.NET Core Module.
The command returns `True` when the x64 preview runtime is installed.
::: moniker range=">= aspnetcore-2.2"
> [!NOTE]
> The platform architecture (x86/x64) of an App Services app is set in the **Application Settings** blade under **General Settings** for apps that are hosted on an A-series compute or better hosting tier. If the app is run in in-process mode and the platform architecture is configured for 64-bit (x64), the ASP.NET Core Module uses the 64-bit preview runtime, if present. Install the **ASP.NET Core <x.y> (x64) Runtime** extension (for example, **ASP.NET Core 2.2 (x64) Runtime**).
>
> After installing the x64 preview runtime, run the following command in the Kudu PowerShell command window to verify the installation. Substitute the ASP.NET Core runtime version for `<x.y>` in the command:
> **ASP.NET Core Extensions** enables additional functionality for ASP.NET Core on Azure App Services, such as enabling Azure logging. The extension is installed automatically when deploying from Visual Studio. If the extension isn't installed, install it for the app.
If an ARM template is used to create and deploy apps, the `siteextensions` resource type can be used to add the site extension to a web app. For example:
A [self-contained app](/dotnet/core/deploying/#self-contained-deployments-scd) can be deployed that carries the preview runtime in the deployment. When deploying a self-contained app:
The [Docker Hub](https://hub.docker.com/r/microsoft/aspnetcore/) contains the latest preview Docker images. The images can be used as a base image. Use the image and deploy to Web Apps for Containers normally.
Azure App Service on Windows Server uses [Internet Information Services (IIS)](https://www.iis.net/). The following topics pertain to the underlying IIS technology:
