What Is an ASPX File?

How to open, edit, and convert ASPX files

What to Know

  • An ASPX file is an Active Server Page Extended file.
  • Open one with your web browser or a text editor like Notepad++.
  • Convert to HTML, ASP, and other similar formats using Visual Studio.

This article explains what ASPX files are and how they're used, what to do if you download one by mistake, and how to convert one to a more usable format.

What Is An ASPX File?

A file with the ASPX file extension is an Active Server Page Extended file that's designed for Microsoft's ASP.NET framework. It's also called a .NET web form. Although they look fairly similar, ASPX files aren't the same as Web Handler files that end in ASHX.

A web server generates these files, and they and contain scripts and source codes that help communicate to a browser how a web page should be opened and displayed.

Person looking at aspx files on a computer

Derek Abella / Lifewire

More often than not, you'll probably only see this extension in a URL or when your browser accidentally sends you an ASPX file instead of the one you thought you were downloading.

How to Open Downloaded ASPX Files

If you've downloaded an ASPX 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.

In that case, one trick is to simply rename it to whatever you expect it to be. For example, if you expected a PDF version of a bill from your online bank account, but instead got a file with this file extension, rename it to bill.pdf and then open that. If you expected an image, try renaming it to image.jpg. You get the idea.

Screenshot showing how to change the file extension of an ASPX file to PDF
Renaming ASPX to PDF.

To rename a file's extension, your computer has to be set up to show the file extension. To do this, open the Run dialog box (WIN+R) and enter control folders. Use the View menu to locate Hide extensions for known file types—uncheck it and apply the changes.

The issue here is that sometimes the server (the website you're getting the file from) doesn't properly name the generated file (the PDF, the image, the music file, etc.) and present it for downloading as it should. You're just manually taking that last step.

You can't always change a file extension to something else and expect it to work under the new format. This case with a PDF file and the ASPX file extension is a very special circumstance because it's basically just a naming error that you're fixing.

Sometimes the cause of this problem is browser or plug-in related, so you might have luck loading the page that's generating the ASPX file from a different browser than the one you're using now. For example, if you're using Edge, try switching to Chrome or Firefox.

How to Open Other ASPX Files

Seeing a URL with ASPX at the end, like this one from Microsoft, means page is being run in the ASP.NET framework:


There's no need to do anything to open this type of file because your browser does it for you.

When the browser displays the page, it looks completely normal; this is what the source code behind the page looks like in that example:

Screenshot of the text behind an ASPX web page
ASPX Sample Text.

The actual code in the file is processed by the web server and can be coded in any program that codes in ASP.NET. Microsoft's Visual Studio is one free program you can use to open and edit these files. Another tool, although not free, is the popular Adobe Dreamweaver. Sometimes, an ASPX file can be viewed, and its contents edited, with one of these free text file editors.

Many URLs end in default.aspx because that file serves as the default web page for Microsoft IIS servers (i.e., that's the page that opens when a user requests the site's root web page). It can, however, be changed to a different file by an admin.

How to Convert an ASPX File

ASPX files have an explicit purpose. Unlike images, like PNGs or JPGs, where a file conversion retains compatibility with most image editors and viewers, ASPX files will stop doing what they're meant to do if you convert them to other file formats.

Converting one to HTML, for example, will certainly make the HTML result look like the ASPX web page. However, since the elements of the ASPX file are processed on a server, you can't use them properly if they exist as HTML, PDF, JPG, or any other file you convert them to.

However, given that there are programs that use ASPX files, you can save one as something else if you open it in an appropriate editor. Visual Studio, for example, can save one to HTM, HTML, ASP, WSF, VBS, ASMX, MSGX, SVC, SRF, JS, etc.

Still Can't Open It?

Be careful to avoid confusing other similarly named file extensions for one that ends with .ASPX.

For example, ASX files look like they might be related to ASPX files, but they could actually be Alpha Five Library Temporary Index files that only work within the context of the Alpha Anywhere platform. The same is true for others like ASCX.

  • How do you open ASPX files on Android?

    To turn an ASPX file into a PDF for viewing on an Android, open the file as normal, go to File > Print and choose to print as a PDF.

  • How do you open an ASPX file on a Mac?

    Microsoft has a Mac version of its Visual Studio software, which allows you to open ASPX files on that platform. Download and install Visual Studio for Mac on Microsoft's website.

  • How do you create an ASPX file using inline code instead of code behind?

    To use inline code, create a new web page on your website in Visual Studio and make sure Place code in separate file is unchecked.

Was this page helpful?