Configure Virtual Applications, Mounted Azure Files, and Static File Access in Azure App Service

Background:

In Azure App Service, developers often need to serve files (images, config files, data files, etc.) that are stored outside the app’s wwwroot folder — such as on an Azure File Share.

This is especially useful when:

• You want to share files across multiple web apps
• Your files are too large to bundle with the app
• You need to manage files independently from the app deployment

To accomplish this, Azure provides the ability to:

• Mount external Azure File Shares into your web app's file system
• Expose those mounted folders via virtual paths
• Configure directory browsing and MIME types to make files directly accessible over the browser

Step-by-Step Configuration:

===Azure Storage Account part===

Create Azure File Share

===Azure App Service part===

1.Mount Azure File Share

Azure Portal → App Service → Configuration → Path Mappings → Mount Storage

• Click + New Azure Storage Mount
• Provide:
• Name: (e.g. fileshare)
• Storage account: Select your storage account
• Storage container: Select your file share name
• Mount Path: (e.g. /mounts/share)

The mounted path will appear as C:\mounts\share in the backend file system (Kudu).

2.Set Virtual Path to Expose via URL

Azure Portal → Configuration → Path Mappings → Virtual applications and directories

• Click + Add
• Virtual Path: e.g. /fileshare (URL access path)
• The Virtual Path is the URL path that users will type in the browser to access a folder or file hosted by your App Service.
• Physical Path: \mounts\share
• The Physical Path (Mount Path) is the actual folder path on the file system where your Azure File Share is located inside the App Service.
• Select Directory

This maps URL path (Virtual Path, like /files) to a specific physical folder (Physical Path, like C:\mounts\share).

3.Verify File Structure in Kudu

Open Kudu: https://<your-app-name>.scm.azurewebsites.net

Go to: Debug Console → CMD → C:\mounts\share

You should see your mounted file share contents (e.g., folders, .jpg, .json)

Common Issues & Fixes

Issue 1: Access Denied When Browsing Virtual Path

Example URL: https://<app>.azurewebsites.net/fileshare/

-> Showing directory listing

Error message from browser: You do not have permission to view this directory or page.

Cause: Directory browsing is disabled by default.

Solution: Create a web.config file under site\wwwroot with:

<configuration>
  <system.webServer>
    <directoryBrowse enabled="true" />
  </system.webServer>
</configuration>

This enables directory listing in browser.

Issue 2: Can't open .json Files

Example URL: https://<app>.azurewebsites.net/fileshare/folder1/AppInit.json

-> Serving .json file correctly

Error message from browser: The resource you are looking for has been removed, had its name changed, or is temporarily unavailable.

Cause: MIME type for .json files is not configured.

Solution: Update web.config to allow serving .json:

<configuration>
  <system.webServer>
    <staticContent>
      <mimeMap fileExtension=".json" mimeType="application/json" />
    </staticContent>
  </system.webServer>
</configuration>

Reference: Configure an App Service App - Azure App Service | Microsoft Learn