What Is an APPLICATION File?

This article describes what an APPLICATION file is and how to open one or convert one to a different format.

What Is an APPLICATION File?

A file with the .APPLICATION file extension is a ClickOnce deployment manifest file. It provides a way to launch Windows applications from a web page with just one click.

The file holds information about application updates by including the name, identity of the publisher, application version, dependencies, update behavior, digital signature, etc.

Files with this extension are seen alongside APPREF-MS files, which are Microsoft application reference files. They are what actually call on ClickOnce to run the application—they hold the link to where the application is stored.

Other Kinds of Application Files

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.

Sometimes regular document, music, or video files are incorrectly referred to as application files, like PDF, MP3, MP4, DOCX, etc. These have nothing to do with the APPLICATION extension.

How to Open an APPLICATION File

APPLICATION files are XML-based, text-only files. This means Microsoft's Visual Studio or even a basic 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 Microsoft's Edge browser. This also means programs like MS Word and Outlook can open the file only if Microsoft's browser is set as the default browser.

How to Convert an APPLICATION File

You should be able to open the file in Visual Studio and then save the open file to another format. Of course, XML editors can do so, too.

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 It?

Files that exist in a completely different format might use a similar-looking file extension, but they really have nothing to do with ClickOnce deployment manifest files. If you can't open your file, re-read the extension to see what you're really dealing with.

For example, APP files may be macOS or FoxPro application files, APPLET files are used by Eclipse as Java Applet Policy files, and APLP is reserved for Audials plug-in packages. APK is another file extension that might be confused for an APPLICATION file.

In any case, if you don't have an APPLICATION file, you'll need to research the extension that you see at the end of your file. That's the only way to dig into what the format is and learn which programs are capable of opening, editing, or converting it.