ASCX File
What are ASCX files and how to open them
Are you having problems opening an ASCX file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your ASCX files.
What is an ASCX file?
An .ASCX file is a Microsoft ASP.NET Web User Control file.
Microsoft ASP.NET Web User Control files define reusable interface components for web applications built with ASP.NET Web Forms. Created and edited within development tools like Microsoft Visual Studio, they store markup (HTML-like content), Web server controls, and optionally embedded or separate code that govern visual and interactive behavior. They allow a single control - such as a navigation bar, form fragment, or footer - to be designed once and included in many web pages, improving maintainability and consistency. Web pages host these controls rather than the controls running on their own.
These controls are compiled at runtime by the ASP.NET framework into classes that inherit from the System.Web.UI.UserControl base class. When a web page (or another user control) includes a user control, ASP.NET parses the markup directives, binds any code-behind class or inline code specified by directives like @ Control, and instantiates the control for rendering. User controls share much of the behavior of full ASP.NET pages - such as event handling, lifecycle methods (Load, PreRender, etc.), and access to intrinsic objects like Request, Response, Session - but they are never requested directly via a URL. Instead they live within host pages that supply the surrounding HTML structure including <html>, <body>, and <form> tags.
Internal identifiers help detect and validate this format. Files begin with an @ Control directive rather than @ Page, and often include keywords such as Language, CodeFile or Inherits. Signature bytes sometimes include ASCII text like "%@" at the start or strings like "CONTROL LANGUAGE" or "INHERITS" inside the file.
How to open ASCX files
Important: Different programs may use files with the ASCX file extension for different purposes, so unless you are sure which format your ASCX file is, you may need to try a few different programs.
While we have not verified the apps ourselves yet, our users have suggested ten different ASCX openers which you will find listed below.
Last updated: August 21, 2026
Various apps that use files with this extension
These apps are known to open certain types of ASCX files. Remember, different programs may use ASCX files for different purposes, so you may need to try out a few of them to be able to open your specific file.
 | Adobe Dreamweaver | User submitted |
 | Macromedia Dreamweaver MX | User submitted |
 | Microsoft Web Platform Extensions | User submitted |
 | progeCAD Professional | User submitted |
 | Xamarin Studio | User submitted |
 | MonoDevelop | User submitted |
 | Untis | User submitted |
 | Microsoft Office | User submitted |
 | Cursor | User submitted |
 | Embarcadero C++ Builder | User submitted |
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