I saw here on the forum few different ways of checking spell: Spell Checker (by iCode) OpenOffice/LibreOffice Spell Checker (by GMK)  v0.1.1 Scite4AutoIt SpellChecker using LibreOffice even few topics about spell checking with Word. Custom Spell Checker But I start wondering how Notepad in Windows 11 finds out that some words are written incorrectly. Then I ask ChatGPT about and he point me to Spell Checking API. https://learn.microsoft.com/en-us/windows/win32/intl/ab