Error Code Portal
MicrosoftWindows Win32Error code

401

ERROR_THREAD_MODE_NOT_BACKGROUND

Alternative forms: 0x00000191 · 0x191 · ERROR_THREAD_MODE_NOT_BACKGROUND · 0x80070191

What does this code mean?

Code 401 · An issue reported by Windows Win32.

Official explanation · Original text

The thread is not in background processing mode.

Troubleshooting and diagnostic links

First check that the document's product, version, and environment match your situation.

Source and terms of use

System Error Codes (0-499) (WinError.h) ↗

Creator: Microsoft and MicrosoftDocs contributors
License: Creative Commons Attribution 4.0 International
Checked on: 2026-11-12

Modifications: Extracted numeric codes, symbolic names and English message text; converted Markdown/HTML to plain text and normalized whitespace; added Korean product context, namespace labels, status classification and separately labeled official links. No machine translation of message text.

Source details · Original licenses and notices