To make Notepad files always open in a new or separate window in Windows 11, open Notepad setting and change the 'Opening files' option.

You can make Text files open directly in Notepad++ instead of Notepad in Windows 11/10. Learn how to make Notepad++ as the default Text Editor.

A CSV file is a simple text file that you can open in a wide variety of programs, including any program that works with plain text like the Notepad app.