How to Open, Edit, & Convert MAS Files

Screenshot of several MAS files in Windows 10 that open with Microsoft Access
MAS Files.

A file with the MAS file extension may be a Microsoft Access Stored Procedure Shortcut file. This format stores a query that has been pre-written and used by a Microsoft Access database.

Another format that uses the MAS file extension is the rFactor Track file used by Image Space's rFactor racing simulation video game, storing information about how the racing track should look. Additionally, some MAS files may include other assets like vehicle and sound data and are sometimes seen alongside MFT files.

If not in either of these formats, an MAS file may instead be a MEGA Alignment Sequence file that stores genetic information, in binary, for use with the MEGA software. This format is used to help align genetic codes between different samples.

How to Open an MAS File

Microsoft Access Stored Procedure Shortcut files open with Microsoft Access.

rFactor is the software that opens rFactor Track files. Some default MAS files are installed in the \rFactor2\Installed\ folder by default. Also available on the rFactor website is gMotor MAS File Utility, a portable program (i.e. you don't have to install it) that opens these kinds of MAS files through its File > Open... menu.

Note: gMotor MAS File Utility is included in the "rFactor mod development tool pack" download, too, which you can also find on their download page. You can either download the whole pack or just the utility itself.

The software used to open MEGA Alignment Sequence files is called MEGA.

You can do this through its Alignment Explorer tool using the Align > Open Saved Alignment Session... menu item. This application may use the MAS file to create other files like MEGA Tree Session files (.MTS).

If these programs don't open your MAS file, you might want to try a text editor like Notepad in Windows, TextEdit in macOS, or some other free text editor program.

When you view a file as a text document, you can often find a word or two that helps you identify the format it's in, which is often extremely helpful in finding an appropriate program that can open that particular file.

Tip: If you find that an application on your PC does try to open the MAS file but it's the wrong application or if you would rather have another installed program open MAS files, see our How to Change the Default Program for a Specific File Extension guide for making that change in Windows.

How to Convert an MAS File

It's unlikely that MAS files that are used with Microsoft Access can be converted to another format, but you can try it to be sure. If it is possible, you'll be able to do so through the File > Save As menu.

If you're looking to convert an MAS file used with rFactor, try looking through the menu for a File > Save As or Export option, which is usually how software programs convert file formats.

While MEGA is used to open some MAS files, it's unlikely that it can convert Alignment Sequence files - they seem to have a limited purpose and so probably aren't meant to exist in any other format. However, again, some sort of "Save" or "Export" menu is what you should look for if you suspect that you can, in fact, convert the MAS file using MEGA.

Still Can't Open the File?

MAS files that still won't open after trying the suggestions above may not even be MAS files. Be sure to double-check that you're not misreading the file extension. 

There are definitely many examples of similarly spelled file extensions that are completely unrelated to MAS files. MAT files are one example.

If your file doesn't use the .MAS file extension, use the search box at the top of this page or go to Google, to learn more about the file extension to see what format the file is in and what program is able to open or convert it.

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