MATLAB Answers


Why is a new instance of MATLAB opened when I double-click on a MATLAB file in Windows Explorer even if I have one instance of MATLAB already open on my Windows 7 machine?

Asked by MathWorks Support Team on 18 Apr 2013
Latest activity Commented on by Ermin Gong
on 16 Nov 2016

I have full administrative privileges on my Windows 7 machine and I run MATLAB as an administrator. I then open a Windows Explorer and double-click on a MATLAB file. I expect the MATLAB file to open in the existing instance of MATLAB, instead another instance of MATLAB is launched, and the MATLAB file opens there in the Editor. If I double-click on another MATLAB file in Windows Explorer, it opens in Editor in the second instance of MATLAB. However, if I close the second instance of MATLAB and then double-click on a MATLAB file in Windows Explorer it will open another MATLAB instance.

I am running MATLAB as an administrator because otherwise I cannot save path from File->Set Path->Save menu. I have User Control Access (UAC) turned on and I cannot turn it off because of security considerations.

3 Answers

Answer by MathWorks Support Team on 10 Nov 2015
 Accepted answer

This behavior may have one of several causes:

A. This may be a consequence of the security settings on Windows 7. When you run MATLAB as an administrator and then try to open a MATLAB file from Windows Explorer, you are not a privileged user as far as Windows Explorer is concerned. As a result, MATLAB that is open cannot open this MATLAB file since MATLAB is a program that is run by a privileged user (administrator).

To work around this issue, you can enable writing to the pathdef.m file. The pathdef.m file is located in the directory:


where MATLABROOT is the result of executing the following in the MATLAB command prompt:


To enable writing to pathdef.m:


 1. Open the directory with pathdef.m in the Windows Explorer, right-click on the file and open "Security" tab.
 2.  Click the "Edit" button to modify permissions.
 3.  Select the user or group that should be allowed to write to pathdef.m, i.e., Users.
 4.  Check the "Write" check box and click "Apply"

If you have previously set MATLAB to be run as an administrator, change it to run it as an ordinary user. You will be now able to save path to the pathdef.m file and each time you click on the MATLAB file, if MATLAB is already open, MATLAB file will be opened in the Editor of the open MATLAB instance.

B. This issue may also arise if you uninstall an earlier release of MATLAB after installing a newer release. The newer release uses a different method to register file associations.

These associations are deleted from the registry when an older release is uninstalled. In this situation, please uninstall the new release and reinstall it.

If the file associations are not correct because you have manually registered the MATLAB file types with Windows Explorer, you can re-associate the MATLAB file types by following these instructions from the MATLAB documentation:

This page explains how to re-register the .MAT extension, but you can follow the same instructions for other file types.

  1 Comment

this solution does not work on my Windows 8.1, Matlab R2011a

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Answer by Shahram Bekhrad on 30 May 2016

Hello. I had the same problem on my win 8.1 and MATLAB but followed thorough with the suggested solution by MathWorks Support Team on top of the page and then followed by the other solution on MATLAB File Association Fix by Patrik Forssén on some other post in the site ( How to restore file association in Matlab 2015a for Windows ) and I think that it is alright now. Now when I double click on a MATLAB associated file IF I have an instance of MATLAB open, It opens the file directly in the editor or MATLAB file importer dialog (depends on the file) and if not it opens an instance of MATLAB and the rest follows.


File Association Fix Worked with R2015a for me! thanks a lot! I was going to shoot my laptop and you saved me lot of money

hi,there download the file association fix,and then run it?

omg, finally figure it out followed the discription, thank you so much, the god knows the time and the energy i have paid, btw, matlab 2016b,win10

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Answer by Farzaneh
on 20 Aug 2014

I am using Matlab R2012b. I have the exact same problem, i.e. each time I want to open a matlab-related file, a new session of matlab is opened, instead of opening that file in the already opened matlab session. I have set full control permission to pathdef.m file. No success. Please help.


What about permissions to the folders and subfolders that contain pathdef.m? Do those also have full control?

If you are a support customer, you can submit your question to MathWorks support via the 'My Service Requests' page which is accessible at

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