Software & Apps File Types What Is an APPLICATION File? How to open, edit, and convert APPLICATION files 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 January 17, 2020 File Types Design Cryptocurrency MS Office Windows Linux Google Drive Apps File Types Backup & Utilities View More Tweet Share Email A file with the .APPLICATION file extension is a ClickOnce Deployment Manifest file. They provide a way to launch Windows applications from a web page with just one click. APPLICATION files hold information about application updates by including the name, identity of the publisher, application version, dependencies, update behavior, digital signature, etc. Files with the .APPLICATION extension are seen alongside .APPREF-MS files, which are Microsoft Application Reference files. These files are what actually call on ClickOnce to run the application—they hold the link to where the application is stored. chokkicx / Getty Images An "application file" is also the term used to describe a file that a program puts on a computer after it gets installed. They're more often called program files and might use the EXE file extension, but either way, they don't necessarily have anything to do with the .APPLICATION file extension. How to Open an APPLICATION File APPLICATION files are XML-based, text-only files. This means that Microsoft's Visual Studio or even any text editor should be able to properly read the file. There are several free text editors that will do the job nicely. .NET Framework is required to actually run .APPLICATION files. ClickOnce is a Microsoft system—they have more information about this type of file through that link. Technically, the Microsoft ClickOnce Application Deployment Support Library is the name of the program that opens .APPLICATION files. It's likely that ClickOnce will only open if the URL is accessed through one of Microsoft's browsers: Edge or Internet Explorer. This also means that programs like MS Word and Outlook can open the .APPLICATION file only if Microsoft's browser is set as the default browser. Sometimes regular document, music, or video files are incorrectly referred to as application files, like .PDF, .MP3, .MP4, .DOCX, etc. These file formats have nothing to do with the .APPLICATION extension. If you find that an application on your computer tries to open the APPLICATION file but it's the wrong application or you'd rather have another installed program open APPLICATION files, learn how to change the default program for a specific file extension for making that change in Windows. How to Convert an APPLICATION File You should be able to open an .APPLICATION file in Visual Studio and then save the open file to another format. Of course, XML editors can also save .APPLICATION files to some other format. However, keep in mind that changing the format to something else means that anything that relies on the .APPLICATION file to function will no longer work as it should in the new format. Still Can't Open the File? Other files formats may use a similar file extension, but they really have nothing to do with ClickOnce Deployment Manifest files. For example, APP files may be macOS or FoxPro application files, and APPLET files are used by Eclipse as Java Applet Policy files.