ERROR_THREAD_MODE_NOT_BACKGROUND 0x80070191

Error code 401 · HRESULT 0x80070191

WINDOWS

The thread is not in background processing mode.

Windows troubleshooting diagram: Device Manager warning and a system file scan
Windows errors: check drivers, system files and Event Viewer, in that order.

What it means

ERROR_THREAD_MODE_NOT_BACKGROUND is a Windows error code (system error 401, returned as HRESULT 0x80070191) reported by Windows. Its official message is: “The thread is not in background processing mode.”

How to fix ERROR_THREAD_MODE_NOT_BACKGROUND

  1. Reboot once — many one-off system codes disappear with a clean restart
  2. Repair system files: 'sfc /scannow' then 'DISM /Online /Cleanup-Image /RestoreHealth'
  3. Find the source in Event Viewer → System: filter for this exact code and open its provider link

Related errors

ERROR_THREAD_MODE_ALREADY_BACKGROUNDERROR_THREAD_NOT_IN_PROCESSERROR_THREAD_1_INACTIVEERROR_THREAD_WAS_SUSPENDEDERROR_PROCESS_MODE_ALREADY_BACKGROUNDERROR_EXTERNAL_SYSKEY_NOT_SUPPORTEDERROR_PROCESS_MODE_NOT_BACKGROUND

Source: Microsoft WinError.h

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