I would like to ediff files (or buffers) A and B, and also A and C. The need arises from the fact that A and B were both forked from C, and I need to merge B into A while checking I'm not destroying any ideas in A\C.

I'm not an experienced diff-er, but I thought I would do this by viewing ediff A,C while merging bits of B in to A.

It seems that when I start the second ediff involving A, it takes over my emacs instance and I can't seem to see the other ediff.

My first thought is to just run two different instances of emacs, but how would you do this?

  • 2
    I haven't ever used this but M-x ediff-files3? May 7, 2015 at 15:09
  • 1
    ediff-files3 or ediff-buffers3 are perfect for this. May 7, 2015 at 16:22
  • Are they? I'm not interested in the difference between B and C. Can you link a tutorial for ediff-*3? I do not know what it does other than display a lot of narrow columns of text with many colours :\ edit: tutorial / instructions May 7, 2015 at 18:16
  • ediff3 is designed to do this.
    – Dan
    Mar 4, 2020 at 6:15

1 Answer 1


No problem. Just use ediff-buffers on A and B. And then use ediff-buffers on A and C.

You will have two different control panels, one for A vs B and one for A vs C. Just put your input focus in one or the other of the two panels (windows) to navigate among the differences it controls.

  • I'll check again if this works, but when I started the second ediff-buffers, it stole focus in the window running the first one, and it appeared to me that it changed the highlighting of A. May 7, 2015 at 15:47
  • 2
    You get the highlighting for both, at the same time. But the control panel for a given pair is what governs which highlighting is used. Select the particular control-panel window you want, then just n n n... etc.
    – Drew
    May 7, 2015 at 16:48

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