How to Always Open macOS Text Editor in Plain Text Mode?

By default, the macOS text editor application opens in rich text mode, which means that it preserves formatting of the text you copy/paste. If you wish to change this to plain text mode for every new document that's opened, then you can do the following:

1. Click on the "TextEdit > Preferences" menu option in the application menubar (on the top-left of the screen) to open the preferences dialog;
2. In the "New Document" tab choose "Plain text" under the "Format" settings;
3. Close the preferences dialog.

Now, when you open a new document, it will always be in plain text mode. This change might not apply to already open windows automatically. To toggle those to plain (or rich) text, you can do either of the following:

• Use the Cmd + Shift + T keyboard shortcut, or;
• Click on the "Format > Make Plain/Rich Text" menu option in the application menubar.

Please note that setting the formatting mode to plain text will not preserve formatting of copy/pasted text.