RSS Viewer Web Part

Fixing SharePoint RSS Viewer Web Part connection errors usually involves resolving proxy blocks, authentication mismatches, or security protocols. Because the web part executes requests directly from the SharePoint server—rather than the end user’s machine—standard browser tests will not reveal the core infrastructure issues causing the connection to fail.

🛑 Error 1: “An unexpected error occurred processing your request”

This error typically points to a proxy server blocking the outbound traffic generated by your SharePoint Web Front End (WFE) servers. The Fix: Update web.config with Proxy Settings Log into your SharePoint WFE servers. Open the web.config file for your specific web application.

Locate the tag and insert your corporate proxy information:

Use code with caution. Save the file and perform an iisreset. 🛑 Error 2: “Proxy Authentication Required”

If you add your proxy settings and immediately hit this secondary error, it means your proxy demands NTLM credentials. The RSS Viewer Web Part exclusively supports Anonymous or Kerberos authentication. The Fix: Create a Network Exclusion

You cannot force the out-of-the-box RSS web part to send NTLM credentials.

Ask your network or IT security team to create an anonymous outbound rule or whitelist the target RSS feed URLs on your firewall/proxy for the SharePoint server IPs.

🛑 Error 3: “The requested feed URL does not exist” or “Protocol Error”

If the URL works perfectly in your computer’s browser but fails in the web part, the remote server hosting the feed is likely rejecting the connection due to protocol mismatches or missing security identifiers. The Fixes:

Force HTTPS: Ensure your feed source uses https:// instead of http://. Modern browsers auto-redirect users to HTTPS, masking the fact that a legacy http:// link provided to the web part is triggering mixed-content blocks.

Verify TLS Versions: If the remote feed strictly requires TLS 1.2 or TLS 1.3, ensure your SharePoint server’s .NET Framework is updated and configured to support these protocol versions.

Address the Missing User-Agent String: The RSS Viewer Web Part leaves the User-Agent HTTP header completely empty. Many modern web application firewalls (WAFs) reject requests lacking user agents. If you control the target feed environment, you must adjust its security rules to accept empty User-Agent strings.

🛑 Error 4: “Feed could not be displayed” (Internal Sub-sites)

When you attempt to consume an RSS feed generated by a sub-site or alternative web application within the same SharePoint farm, you may receive an access denied loop. The Fix: Disable or Configure the Loopback Check

This is triggered by the Windows Server Loopback Check feature, which blocks a server from routing web requests back to itself using a fully qualified domain name (FQDN).

Open the Registry Editor (regedit) on the SharePoint server.

Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0

Create a new Multi-String Value named BackConnectionHostNames.

Add the local hostnames/URLs of your SharePoint sites to the text field.

Alternatively, disable the check entirely in development environments by creating a DisableLoopbackCheck DWORD value set to 1 under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa. 🛑 Error 5: “Authenticated feeds are not supported”

If you are using SharePoint Online (Microsoft 365), the modern RSS web part is strictly built for public consumption.