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SourceTree - external diff tool doesn't launch and conflicts disappear

Gilly Dekel Aug 17, 2014


I am using SourceTree with Xcode's FileMerge. This has always worked fine. Today, when I right click->resolve using external diff tool, I get a window for a second showing that the launch is happening, and then nothing and the conflict disappears as though resolved. This is really bad as I am unable to merge changes.

Going into preferences, I tried to change the diff tool, but I can't click on any of the values - everything seems to be locked.


14 answers

29 votes
Victor Ramiro Jan 12, 2017

I had the same problem, it turns out it was an Xcode problem

Run: sudo xcode-select -s /Applications/


Andrea Ciani Sep 18, 2017

This worked for me

Yogesh Randhawa Jan 26, 2018

This worked for me

Alexey Shklyaev Jan 31, 2018

Yes that worked for me, using FileMerge

Daniel Marcotte Feb 17, 2018

I have no idea what this command is doing, but it fixed my problem. Thank you.

Roelof Koelewijn Mar 27, 2018

Super! this works for me.

Riley Hooper Jul 06, 2018

Worked for me running SourceTree 2.7.6 (177) and Xcode 9.4.1.

Toni Firnandes I'm New Here Jan 02, 2019

Thanks, solved by run that magic command.

Rodrigo S. Chavarria Rivera I'm New Here Jan 23, 2019

It works great for me, perfectly

Becca Owens I'm New Here Jan 29, 2019

Worked for me. Thank you!

Gabriele Trabucco Mar 29, 2019

I came from a clean Mac Installation ... As you said I found the command line tool was not properly configured. Nice catch! Thanks

Rich Mucha I'm New Here Apr 26, 2019

Worked for me! Thanks

10 votes
Balazs Szakmary Aug 31, 2014
  • When the diff tool is not (correctly) configured, it behaves the way you described. (not very informative...)
  • In Tools\Options\General, you need to enable "Allow SourceTree to modify your global config files" at the top before you can change the Diff settings.
  • If you have the Diff / Merge tools set to "System default" (this is the default setting), it seems to never work.

So I think what you need to do is:

  1. enable the "Allow..." option
  2. change the diff tool to explicitly specify the right tool with the right cmd options
Duarte Molha May 28, 2015

This is still not working for me. THe external diff tool does not launch!

Trung Duy Van Oct 26, 2015

Thanks. It work perfect

Hussien Khayoon Mar 03, 2016

In Mac, I had to go to SourceTree/Preferences/General


Lynna Landstreet Mar 15, 2016

This did not work for me. That option is checked, Diff/Merge tool is set explicitly to FileMerge (which is what it was using before it abruptly stopped working), and as recommended in another answer here, I have it set to Embedded Git rather than System Git, but none of that helped at all.

It used to work fine, and then suddenly stopped working a while back, without my having changed any configuration options whatsoever. I'm guessing it was when SourceTree automatically updated itself or something... But anyway, none of the answers in this post have helped for me.

Like # people like this
6 votes
Jeff McKnight Feb 20, 2018

Tested with Sourcetree v2.7.1 and DiffMerge v4.2.1 (with command line tools) on MacOS v10.13.3:

1. Open Sourcetree prefs and select `Diff` tab

2. Set `Visual Diff Tool` menu to `Custom`

3. Set `Diff command` field to: /usr/local/bin/diffmerge

4. Set `Arguments` field to: $LOCAL $REMOTE

5. Close prefs, select External Diff (or cmd-D) and observe DiffMerg launches.


More info here:

Anjan T Feb 22, 2018 • edited

You can do the same for "Merge Command" too.

Merge Command:



--merge --result="$MERGED" "$LOCAL" "$BASE" "$REMOTE"
Like # people like this
Jeff McKnight Sep 07, 2018 • edited


4 votes
Joshua Wojcik Aug 12, 2015

I found changing to the Embedded Git rather than System Git fixed the problem.

sean bzd Sep 25, 2015

this resolved my issue as well

Altaf Navalur Nov 29, 2017

this resolved my issue as well. I had tried with DiffMerge & Beyond Compare. Switching to System Git fixed it for me

Thomas Luong Jul 25, 2018

This resolved my Issue.

4 votes
Jeremy Stafford Jul 18, 2016

None of these worked for me either. Using latest SourceTree with Beyond compare. It doesn't happen on every file. I don't know what the common factor is on the files that it does happen with. 



So it turns out the two files I was just trying to merge, the difference was that the file was no longer existent on the remote server. Rather than do something about the merge to show it was deleted, it just hung forever.

jorge granados Feb 14, 2017

This was the right answer. Files no longer exist on remote server. 

Chris Robichaud Jan 24, 2019

Was the solution for me as well. Can't believe there wasn't a simple error message or something, I spent a lot of time trying all of the other solutions, changing settings, etc

Matt Brand Mar 04, 2019

This was what was happening for me. No diff = nothing happens.

1 vote
Sean Chon Aug 23, 2016

Same problem here. I had to accept the user agreement in the terminal before it would launch from SourceTree. Running 'sudo opendiff' worked for me.

Val Gorbatyuk Sep 21, 2016

 This was it for me

1 vote
권상구 Dec 17, 2016

I had same problem.

  1. open your git global config file.
  2. check syntax error.

then I can fix the problem.

I think this is sourcetree bug.

Kevin Condon Apr 19, 2018

Yup, the path to diffmerge had part of it duplicated. Fixing it did the trick. Thanks!

0 votes
Noam G Dec 06, 2015

Hi Yair,

I had the same problem.

As Balazs said, it was because the "System default" was selected for the merge tool. Download a tool and set it as your resolving tool.

0 votes
Brad Curran Jul 05, 2016

If none of these things work, try running `opendiff` in the Terminal. 

It there's an error like below you need to do one of two things: 

  • Install XCode
  • Install another diff program

As of writing SourceTree supports the following programs:

  • Araxis Merge
  • Beyond Compare
  • BBEdit
  • DiffFork
  • DiffMerge
  • Changes
  • FileMerge
  • Kaleidoscope
  • KDiff3
  • P4Merge
  • TextWrangler



0 votes
Gareth Jones May 09, 2017

The fix is yet to arrove but there's a workaround at

0 votes
Jeff Sorrentino Apr 02, 2018

As a workaround I changed the name of my external diff app from




Thus my diff command becomes


with arguments

Jonathan Oliver Nov 07, 2018

Even when I edited the .gitconfig diff tool path and fixed it by removing portion of the path, each time I'd restart DiffMerge, it would reappear.


So, here's the workaround.

1. Symlink DiffMerge to another location (so it's not auto-detected as DiffMerge)

ln -s /Application/ /Applications/

2. Then select a custom diff and merge tool arguments.

Diff command arguments:

--nosplash "$LOCAL" "$REMOTE"

Merge tool arguments:

--merge --result="$MERGED" "$LOCAL" "$BASE" "$REMOTE"

Screen Shot 2018-11-07 at 7.03.22 PM.png

After this, SourceTree will no longer mangle the path at startup because it doesn't think it's DiffMerge anymore.

0 votes
Femi Ojemuyiwa Nov 02, 2018

Nothing above works anymore for diffmerge. Is there going to be a fix in next release or shall we just try any and every solution?

Jonathan Oliver Nov 07, 2018

I just posted a reply above that works as off SourceTree v3.0

0 votes
Becca Owens I'm New Here Mar 29, 2019

I was experiencing this as well, and discovered I'd had a derp moment. The file I was trying to merge had been deleted, therefore there was nothing to merge. :\

0 votes
Patrick Galbraith I'm New Here Apr 10, 2019

I had this issue on Windows. The problem was caused by an upgrade that inserted backslashes "\" into the merge command arguments.

\"$LOCAL\" \"$REMOTE\"

Should be changed to:

Eric Bachtal I'm New Here Jun 06, 2019

Ooooooh!  A winner!  It's been months since external diff worked, I'd been through all the suggestions, saw those slashes but figured it was some sort of necessary string escaping and never considered that might be the cause.  Thank you!

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