What is an ASMX File?

How to Open, Edit, & Convert ASMX Files

Picture of the ASMX file icon

An abbreviation for Active Server Method File, a file with the ASMX file extension is an ASP.NET Web Service Source file.

Unlike ASP.NET web pages that use the .ASPX file extension, ASMX files function as a service that doesn't have a graphical user interface and instead is used to move data and perform other actions behind the scenes.

How To Open an ASMX File

ASMX files are files used with ASP.NET programming and can be opened with any program that codes in ASP.NET (like Microsoft's Visual Studio and Visual Web Developer).

You might also be able to use Notepad++ or another text editor to open an ASMX file for editing.

ASMX files are not intended to be viewed or opened by the browser. If you've downloaded an ASMX file and expected it to contain information (like a document or other saved data), it's likely that something is wrong with the website and instead of generating usable information, it provided this server-side file instead. Try renaming the file to the correct extension as a short term fix.

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

You might be able to use one of the Microsoft programs I mentioned above to convert an ASMX file to another format.

Here's some information on migrating ASP.NET Web Services to the Windows Communication Foundation (WCF) platform. This is useful if you need to use .NET 2.0 services under .NET 3.0.

You can learn how to create a Web Services Description Language (WSDL) file from an ASMX file with this WebReference guide.

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