Why is my Windows 11 file server search so slow and how do I fix it?

Did the November 2025 update break your SMB network search in Windows 11?

System administrators and power users facing severe latency when searching network shares on Windows 11 can now implement a permanent solution. Microsoft has released a fix for the file server search bug introduced in November 2025. If your organization relies on SMB shares, immediate attention to the latest preview update is recommended to restore productivity.

The Root Cause: Indexing Failure on SMB Shares

The core issue manifests as a near-complete failure of the Windows Search Indexer when accessing remote file servers. Instead of utilizing the pre-built index for instant results, File Explorer resorts to a manual, file-by-file crawl. On servers hosting terabytes of data, this behavior renders the search function unusable, with results appearing only after significant delays.

Timeline of the Defect

The performance degradation followed a specific trajectory through recent update cycles:

Origin (October 28, 2025)

The flaw first appeared in the optional preview update KB5067036. Early reports indicated that searching domain-joined file servers under Windows 11 25H2 became practically impossible, as the system ignored server-side indexes.

Escalation (November 11, 2025)

The issue became widespread with the mandatory security update KB5068861. This rollout affected all systems running Windows 11 versions 24H2 and 25H2. Because security updates are often automatically applied, many organizations lost efficient search capabilities overnight without a known workaround.

The Solution: Install Preview Update KB5070311

Microsoft resolved this specific indexing failure with the release of the cumulative preview update KB5070311 on December 1, 2025. Although initially scheduled for late November, the slight delay ensured the inclusion of the necessary patch.

Release Note Confirmation

Microsoft’s documentation for KB5070311 explicitly states:

“[Search indexer] Fixed: This update addresses an issue where File Explorer might not search certain SMB (Server Message Block) shares after the latest updates.”

Verification and Field Results

Deployment of KB5070311 has yielded immediate performance improvements in varied technical environments. Testing confirms that the patch restores normal search speeds in the following configurations:

• Windows 11 Professional clients connected to Windows Server 2019 domains.
• Windows 11 clients accessing QNAP NAS network shares.

Action Item

To resolve the slow search issue, navigate to Settings > Windows Update and manually check for updates. Locate and install 2025-11 Preview Update (KB5070311). A restart will be required to finalize the repair of the search indexer.