What does Windows error code 1407 (ERROR_CANNOT_FIND_WND_CLASS) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: the requested window class cannot be resolved for window creation.

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ERROR_TLW_WITH_WSCHILD	ERROR_WINDOW_OF_OTHER_THREAD

ERROR_CANNOT_FIND_WND_CLASS

USER32 cannot resolve the requested window class

Every created window belongs to a window class. The class can be a predefined system class or an application class registered with RegisterClass or RegisterClassEx. Class lookup also involves the registering module instance.

Typical causes are spelling/encoding mismatches in the class name, creating the window before registration, using the wrong HINSTANCE, or unloading a DLL whose registration/lifetime assumptions were incorrect. An atom returned by class registration must also be passed in the documented atom form.

What to check

Log the class name or atom and hInstance passed to CreateWindowEx.
Verify that registration succeeded in the same process before creation.
Check ANSI/Unicode build paths so the class name is identical at registration and creation.
For DLL-defined classes, make registration and explicit unregistration part of module lifecycle.

ERROR_CLASS_DOES_NOT_EXIST is a class-management status; this page focuses on class resolution while creating or locating a window class for USER32 use.

References

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