STATUS_FORMS_AUTH_REQUIRED 0XC0000905 Fix

This error means Windows is rejecting access to a network resource because it needs forms-based authentication, which Windows itself doesn't support. Fix it by switching to a direct URL or VPN connection.

Quick Answer

This happens when Windows tries to access a network path (like \\server\share) that's actually behind a web server using forms authentication—Windows Explorer expects NTLM or Kerberos, not a login page. Connect via a direct URL or VPN instead.

What's Actually Happening Here

The error code 0XC0000905 maps to STATUS_FORMS_AUTH_REQUIRED. Windows throws this when you type a UNC path (\\server\share) or map a network drive, but the server responds with a redirect to a login page—typically an IIS or SharePoint site using forms-based authentication. Windows Explorer can't handle HTML login forms. It wants a simple NTLM challenge or Kerberos ticket. The server says "go log in via that web page," and Windows says "I don't do that."

You'll see this most often when trying to access a file share that's published through a web application gateway, a SharePoint document library exposed as a network drive, or an old IIS server with forms auth enabled on a directory. I've hit it on Windows 10 22H2 and Windows 11 23H2 connecting to a SharePoint 2019 site.

Fix Steps

Open the folder directly via the web URL. Skip the UNC path entirely. If the share is at \\server\docs, try typing https://server/docs into Windows Explorer's address bar. This forces Windows to use the webDAV redirector, which does handle forms-based login prompts. You'll see the login page as a popup in Explorer. Enter your credentials there.
Map the drive using a web address. Right-click This PC, select "Map network drive," then in the Folder field enter https://server/docs. Check "Connect using different credentials" if needed. Windows will prompt you for the forms-based login. This works because the WebClient service (webDAV) intercepts the request instead of the SMB stack.
Make sure the WebClient service is running. Open Services.msc, find "WebClient," set it to Automatic, and start it. Without this, step 2 fails silently. If the service won't start, check that the "WebDAV Redirector" feature is installed under Windows Features.
If the server is remote, connect via VPN first. Some servers block direct webDAV access from outside the LAN. Connect to your company VPN, then retry step 2. The authentication prompt should now reach the forms page properly.

Alternative Fixes If the Main One Fails

These don't always work, but they've saved me a few times.

Add the server to Trusted Sites in Internet Options. Go to Internet Options > Security > Trusted Sites > Sites. Add the full URL (https://server). This helps older IIS forms auth work with WebClient. It's a long shot, but worth trying after step 2 fails.
Enable Basic Authentication on the server side. If you control the server, open IIS Manager, select the site, double-click Authentication, enable Basic Authentication, and disable Forms Authentication for the share path. Then restart IIS. Now Windows can authenticate using your username/password directly. You'll lose the fancy login page, but the UNC path will work.
Use a third-party tool like SMBDrive or NetDrive. These tools handle webDAV with forms auth better than Windows does. They're not free, but they work when nothing else does.

Prevention Tip

If you're an admin setting up shares for end users: don't mix forms-authenticated web apps with SMB file shares. Pick one model. If you need web access, stick to webDAV with Basic or Windows Authentication. If you need traditional file sharing, use a proper SMB share behind a VPN—no forms auth. This error is a design mismatch, not a bug. Plan your infrastructure to avoid it.