You want a simple, pure-text editor on Mac that works exactly like old Windows Notepad — meaning:

Great news — you have multiple perfect solutions on macOS.

✅ The Best “Old Notepad-Style” Options for Mac

1. TextEdit (built-in) — Make it behave EXACTLY like Notepad

macOS TextEdit supports rich text by default, but you can force it to always open in pure plain text mode.

Open TextEdit
Go to TextEdit > Settings
Select New Document
Under Format, choose Plain Text
Go to the Open and Save tab
Turn ON:
- ✓ Ignore rich text commands in HTML files
- ✓ Display HTML files as HTML code instead of formatted text

✔ No bold
✔ No colors
✔ No font sizes
✔ No rich-text paste
✔ No styling ever

If you want something even cleaner:

Why it's perfect:

Why people love it:

macOS has a built-in shortcut:

This pastes WITHOUT formatting in many apps (Chrome, Safari, Notes, Slack, etc.)

If you want global control:

Now Command+V will ALWAYS paste plain text everywhere.

If you want a browser tool:

Paste → formatting removed.

Based on your message:

“I want 1 editor like old Notepad where I paste anything and it removes all formatting automatically.”

I recommend:

Both behave exactly like old Windows Notepad.