I can not find a settings in TextEdit to disable line wrap. I have found only wrap to page/window.
This isn't possible and you can't even dig into the plist file to override this behaviour. But you can get close.
In File → Page Setup create a Custom Page size with absurdly huge margins:
Now select Format → Wrap to Page and TextEdit will now have horizontal scroll bars, but you'll be stuck with an annoying whitespace on the top and left side of the page.
Another suggestion is to try smultron.
I don't think textedit is designed to be much more than demoware.
I know that this does not answer your question, but let me suggest you TextWrangler as a free and more featured alternative to TextEdit.
Hope it helps.
There's actually a weird bug/behavior in TextEdit on Mac which frustrates me to no end! If you zoom in or out in TextEdit, it breaks the word-wrapping feature, dead.
In other words, to get the behavior you want, simply do the following:
- View -> Zoom Out
- View -> Zoom In
- If not on 'Format -> Wrap to page', switch to it first*
- Format -> Wrap to Window *
(* This is because you have to toggle in and out of 'Wrap to Page')
Bam. No more word-wrapping.
Just tested this on both High Sierra and even Mojave. Same thing. Set that up as a macro using Automator and you can execute it from the services menu or even via a keyboard shortcut.
The down-side is there's no way to re-enable it short of selecting everything, then pasting it into a new document, or saving, then re-starting.