How to make nano act like vi when it comes to text wrapping

If you press Ctrl+U immediately after Ctrl+J, the justification is undone. Nano in fact tells you (the ^U shortcut description at the bottom changes from UnCut Text to UnJustify). No, I won't blame you for not noticing that. You can't unjustify if you've typed anything after Ctrl+J. Yes, that's pretty underwhelming (far from a general undo).

To see the word wrapping style you described, use nano's "soft wrapping": Esc+$.

The Esc+L command you (and everyone) tried does "hard wrapping."

Note on keystroke notation - if you are new to Linux, the notation Esc+$ means press and release Esc and then press $. The full key press sequence then is Esc, Shift+4.

(It does not mean hold down escape while pressing $.)

_{Source: https://www.nano-editor.org/dist/v2.9/nano.html (search for --softwrap)}

Note on softwrap and formatting mistakes - If you are new to nano, be a little careful of softwrap. If you are editing a configuration file or something else that is sensitive to newlines or indents, formatting mistakes can be made. Until you get comfortable with softwrap’s behaviors, I suggest doing a quick check with softwrap off (do the key sequence again) before saving.

Note on the goodness provided by others in their answers below - because different operating systems and different versions of nano do things a little differently:

• If you like softwrap on all of the time, set it in your .nanorc, as described in x0a's answer below, as it is a bit more through than Prashant's.
• If you have a Raspberry Pi, note chainsawmascara's answer about needing an extra keystroke for softwrap to go into effect.
• If you have a Mac, like lodeOfCode's answer below, you can always update nano and here, and thus bask in the warm glow of softwrap!

nano linewrap