Check spelling and grammar in TextEdit on Mac
You can check spelling and grammar as you type.
In the TextEdit app on your Mac, choose TextEdit > Settings, then click New Document.
Under Options, select one or more spelling or grammar options.
If you click Restore All Defaults in the New Document pane, these options are set to match the spelling and grammar settings in Keyboard settings. To adjust these settings, choose Apple menu > System Settings, then click Keyboard. (You may need to scroll down.) Go to Text Input on the right, click Edit, then change any spelling and grammar settings.
Note: If you change Keyboard settings while TextEdit is open, you must quit and reopen TextEdit before clicking Restore All Defaults in the New Document pane.