Software & Apps File Types What Is an ADMX File? By Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated May 30, 2019 File Types Design Cryptocurrency MS Office Windows Linux Google Drive Apps File Types Backup & Utilities View More Tweet Share Email A file with the ADMX file extension is a Windows/Office Group Policy Settings XML-based file that serves as a replacement for the older ADM file type. Introduced in Windows Vista and Windows Server 2008, ADMX files — sometimes called Administrative Template XML-Based files — specify which registry keys in the Windows Registry are changed when a certain Group Policy setting is changed. For example, one ADMX file might prevent users from accessing Internet Explorer. The information for this block is located in the ADMX file which in turn is reflected in the registry. How to Open an ADMX File ADMX files are structured the same as XML files and so you can follow the same open/edit rules. In other words, any text editor, like Notepad in Windows or the free Notepad++, will open ADMX files for viewing and editing. If you're using a Mac or Linux computer to read or edit the ADMX file, Brackets or Sublime Text might work, too. Microsoft's ADMX Migrator tool is a free add-on to the Microsoft Management Console (MMC) that provides a GUI to edit ADMX files instead of you having to use a text editor. Viewing an ADMX file using a text editor is for that purpose only — to view the ADMX file. You don't need to open ADMX files manually for them to be used because the Group Policy Management Console or Group Policy Object Editor is what actually utilizes the files. ADMX files are located in the C:\Windows\PolicyDefinitions\ folder in Windows; this is how you can import ADMX files into your computer: copy them to that folder. To display policy settings in a specific language, ADMX files reference language-specific resource files (ADML files) in a subfolder in the same location. For example, US English Windows installs use the en-US subfolder to hold ADML files. If you're on a domain, use this folder instead: C:\Windows\SYSVOL\sysvol\[your domain]\Policies You can read more about using ADMX files to manage group policy, and about the differences between ADMX files and ADML files. How to Convert an ADMX File There aren't any clear reasons, or means for that matter, to convert an ADMX file to another file format. However, you may be interested in converting another type of file to an ADMX file. In addition to editing ADMX files, the free ADMX Migrator tool from Microsoft can convert files from ADM to ADMX. Since ADMX files define which registry keys should be changed in order to apply a Group Policy setting, it would follow that you could convert REG files to a format that could be used by Group Policy. That procedure uses a script in Microsoft's Visual Studio program to convert REG to ADMX and ADML. More Information on ADMX Files Group Policy Object Editor in versions of Windows and Windows Server prior to Vista and Server 2008 are unable to display ADMX files. However, all operating systems that use Group Policy are able to work with the older ADM format. Internet Explorer template files are stored in a file called inetres.admx. You can download Internet Explorer Administrative Templates from Microsoft, too. Still Can't Open Your File? The first thing you should check for if the file isn't opening with any of the suggestions above, is that the file extension actually does read as ".ADMX" and not just something that looks similar. For example, ADX is often confused for ADMX but is used for Approach Index files or ADX Audio files; neither of which have anything to do with Group Policy or the XML format in general. If you have an ADX file, it either opens with IBM's Lotus Approach or is played as an audio file using FFmpeg. If it's not clear already, the idea here is to just make sure that the file you're trying to open is actually using a file extension supported by the software. If you don't really have an ADMX file, then research the file's true extension to learn more about which programs can open or convert it.