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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
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.
  1 Comment
Image Analyst
Image Analyst on 1 Aug 2019
Note that the Mathworks Support Team answer for Windows 10 does not work. For example, there is no Programs in Control Panel. I see a differently-named sequence of steps. Nor is there any "Open with..." option that some people meantioned. What you need to do is:
  1. Left-click the Start button and left-click the gear to bring up Control Panel.
  2. Left-click on the Apps icon (not Programs, which doesn't exist on my computer)
  3. On the left hand panel, left-click "Default apps"
  4. Scroll down a bit past some icons and click on the blue text "Choose default apps by file type"
  5. If you're lucky, you'll see something like FIgure 1 below. In that case click on the Access icon and then select MATLAB from the list of apps that appears. If you're not lucky, then you'll see figure 2 below and you will have no opportunity to select MATLAB.
Note: Figure 2 is from a computer that has had the MATLAB Runtime Library installed (MCRInstaller.exe), but not the MATLAB development environment.

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