On Thu, Oct 21, 2021 at 09:23:35AM +0000, tolugboji via Users list for the GNU Emacs text editor wrote:
> I want to see differences between two files side-by-side (one on a left window, the other on a right window).
> The purpose is not simply see the differences side-by-side, but also to make modifications on each window
> and be able to show differences again.
> 
> Is such a thing possible to do in emacs?

M-x ediff  :)

You can diff two files, a file with a buffer... Side by side, top
to bottom, whatever.

There is documentation for the ediff mode. Try C-h i ediff, perhaps it is
installed on your machine. If not (and if you want to suffer the whims
of your browser ;-) it's on the internets [1] too.

Cheers

[1] https://www.gnu.org/software/emacs/manual/html_mono/ediff.html

 - t