Are Windows window classes case-sensitive?

Question

MS docs being clear as mud (and the class name strings not referenced very often), I was wondering whether the class name of a Win32 window class is actually case sensitive?

Answer 1

They are not case-sensitive. Window class names are string ATOMS, and according to MSDN,

• Case is not significant in searches for an atom name in an atom table. Also, the entire string must match in a search operation; no substring matching is performed.
• The string associated with a string atom can be no more than 255 bytes in size. This limitation applies to all atom functions.