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Why have all my MAT-files become associated with Microsoft Access?

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Whenever I open a MAT-file outside of MATLAB, it opens with Microsoft Access. I would like to associate MAT-files with MATLAB.

Accepted Answer

MathWorks Support Team
MathWorks Support Team on 21 May 2020
Edited: MathWorks Support Team on 21 May 2020
Information relevant to this issue can be found in the documentation at the following link:
This behavior occurs after installing Microsoft Office. The .mat extension becomes associated with Microsoft Access if you do not deselect this option during Access installation.
Microsoft Office causes the *.mat files to appear as shortcuts and not as actual files to Windows.
If you are using Microsoft Windows 10, you can restore the file associations with the following steps:
1. Open 'Control Panel'. This can be done most easily from the Start menu or by searching for it
2. In the ‘Control Panel’, click on 'Programs' section, then on the next page, click 'Default Programs'
3. Click on 'Associate a file type or protocol with a program' then scroll down and click on 'Choose default apps by file type'
4. On the next page, you will see a list of file extensions with their associated default programs. Find the MAT file extension then click on either the plus sign or the current associated application to its right.
5. There will be a pop-up menu where you can select to associate the MAT file with MATLAB
If you are using Microsoft Windows Vista or 7, you can restore the file associations with the following steps:
1. Click the Windows Start menu.
2. Select Control Panel.
3a. If the Control Panel view is set to "View by: Category" in the top right, navigate to: Programs > Default Programs >Associate a file type or protocol with a program
OR
3b. If the Control Panel view is set to "View by: Small icons" or "View by: Large icons" in the top right, navigate to: Default Programs >Associate a file type or protocol with a program
4. After the Set Associations window populates, scroll down to the .mat option.
5. Click it, and then click on "Change Program" on the top right corner.
6. Select MATLAB. If MATLAB is not listed in the program list, click on "Browse" then search for the MATLAB application, which is located in the MATLABROOT folder. On a Windows machine, this is usually C:\Program Files\MATLAB\R20* where R20* is the version of MATLAB.
7. Click Close to close the Set Associations window.
8. All MAT files will now open with MATLAB.
If you are using MATLAB on Microsoft Windows XP, read below for instructions:
1. From a Windows Explorer window, select "Tools -> Folder Options -> File Types".
2. Now select 'New'.
3. Enter the MAT extension in the text box.
4. Click 'Advanced' and from the List Box select 'MATLAB data file' or 'MATLAB MAT-file'.
5. After making this change, you will be able to use the "Change" button on the File Types dialog to make further changes such as selecting a specific MATLAB release.
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More Answers (7)

MMBB
MMBB on 6 Feb 2018
I am having the same problem. My .mat files are associated with Access which I can't uninstall as it's part of the Microsoft package (I'm using a lab computer). Matlab is not recognized in the default apps section (only options are Access or something from the App store) as it is a third party program. There is no 'open with' option on the .mat files but even if there was, I have no idea which folder I am to navigate to (when I go to C:\Program Files\MATLAB\R2017b, I don't know what to choose). Any help would be greatly appreciated!!!!
  2 Comments
Kendall Copp
Kendall Copp on 13 Jul 2018
Hey MMRB and NAVTHA SAI, I don't know if you're still looking for a solution, but I have made a little progress. See my comment on Mathworks Support Team's answer above.
Edit: direct link to my comment: https://www.mathworks.com/matlabcentral/answers/103000-why-have-all-my-mat-files-become-associated-with-microsoft-access#comment_589163

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Jelena Ponocko
Jelena Ponocko on 30 Jun 2016
For Miscrosoft Office 2010, after you open your folder with access files, select one of them and just click on the arrow next to Microsoft Access icon on the top and choose Matlab as the default program - worked for me.

Al in St. Louis
Al in St. Louis on 19 Nov 2018
I have Office 365 and Windows 7. I've reset my default program to MATLAB a few days ago, but Office hijacked the .MAT files again. I have to assume this occurs during an Office Update installation.


Furkan Ümit Sözen
Furkan Ümit Sözen on 27 Mar 2020
I do everything what it says but it did not work. Can anyone please help me? I use R2018b. Should i uninstall it and install R2020a? Do you think it wil work?
  1 Comment
Al in St. Louis
Al in St. Louis on 27 Mar 2020
I have given up on this. As best I can tell, Microsoft resets .MAT files with every Office Update that gets installed. It's annoying, but it is what it is. The only effect is when I'm looking at files in a folder, and the filetype is displayed incorrectly. Microsoft defeated Mathworks in this petty squabble.

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Mark Kelfer
Mark Kelfer on 7 Aug 2020
Edited: Mark Kelfer on 7 Aug 2020
Ok, Here's how to prevent Windows from treating *.mat as a link (preventing the 'open as...' menu).
You need to go to the registry (start -> run -> regedit) and go to Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Access.Shortcut.Table.1
delete the NeverShowExt and the IsShortCut keys
reboot
Thats it, hope this helps.

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