What Is an MDW File?

How to Open, Edit, & Convert MDW Files

MDW Files
MDW Files.

A file with the MDW file extension is a Microsoft Access Workgroup Information file, sometimes just called a WIF (workgroup information file).

An MDW file stores the usernames and passwords for users and groups that should have access to a particular MS Access database, like an MDB file.

While the credentials for a database are stored in the MDW file, it's the MDB file that holds the permissions that the users are granted.

How to Open an MDW File

MDW files can be opened with Microsoft Access.

Note: The user-level security that MDW files provide are for MDB files only, so they're not available for use with newer database formats like ACCDB and ACCDE. See Microsoft's What happened to user-level security? for some additional information on that.

If Access isn't opening your MDW, it's possible that your specific file isn't a Microsoft Access file at all. This is because other programs may use the .MDW file extension too, but to hold information other than database credentials like with the WIF.

For MDW files that aren't Microsoft Access Workgroup Information files, use a free text editor to open the MDW file as a text document. Doing this might help you find some sort of information within the file itself that can explain the program that was used to create it, which can help you track down a compatible MDW opener.

Note: The MDW format used with MS Access has nothing to do with the MarinerWrite Document format that uses the .MWD file extension. Even though their file extensions are similar, MWD files are used with Mariner Write, not Microsoft Access.

If you find that an application on your PC does try to open the MDW file but it's the wrong application or if you would rather have another installed program open MDW 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 MDW File

If your MDW file was created in Access 2003, you can open it in a newer version through the command line. See this thread at Stack Overflow for specific instructions on opening an Access 2003 MDW file in Access 2010. Similar steps could be taken for a version newer than Access 2010.

For MDW files that aren't associated with Microsoft Access, the program that created it is most likely able to convert it to a new format. This is usually possible through an Export menu of some kind.

Additional Reading on MDW Files

If you're securing an MDW file to prevent access to it, it's important to create a new file altogether instead of using the default MDW file that comes with Microsoft Access. This is because the default file, called System.mdw, stores the same default credentials for accessing the database, on any and all computers that use Microsoft Access, meaning it's not at all secure by default.

Therefore, you shouldn't use the MDW file that Microsoft supplies with Access, but instead should create your own. You can build your own custom MDW file in MS Access through the Tools > Security > Workgroup Administrator menu.

It's also important to always keep a backup of an MDW file so that you can avoid having to re-create all the user/group accounts that existed in the file, if you happen to lose it.

Building the file from scratch is a delicate process that must be done perfectly or you won't be able to access the database with the WIF.

Microsoft has some more information the role of MDW files in Access security.

More Help With MDW Files

See Get More Help for information about contacting me on social networks or via email, posting on tech support forums, and more. Let me know what kinds of problems you're having with opening or using the MDW file and I'll see what I can do to help.

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