What is an APPLICATION File?

How to Open, Edit, & Convert APPLICATION Files

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A file with the .APPLICATION file extension is a ClickOnce Deployment Manifest file. They provide a way to launch Windows applications from a webpage 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 is 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.

Note: 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, 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, like Notepad++, should be able to properly read the file. You can learn more about XML files here: What is an XML File?

.NET Framework is required to actually run .APPLICATION files.

ClickOnce is a Microsoft system - they have more information about this type of file here: ClickOnce Deployment Manifest. Technically, the Microsoft ClickOnce Application Deployment Support Library is the name of the program that opens .APPLICATION files.

Note: It's likely that ClickOnce will only open if the URL is accessed through Internet Explorer. This also means that programs like MS Word and Outlook can open the .APPLICATION file only if Internet Explorer is set as the default browser.

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.

Note: Keep in mind what I said above about general "application files." Also, 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 PC does try to open the APPLICATION file but it's the wrong application or if you would rather have another installed program open APPLICATION files, see my How To Change the Default Program for a Specific File Extension guide 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.

More Help With APPLICATION 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 APPLICATION file and I'll see what I can do to help.