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OCX File

OCX is short for OLE Control Extension and it is a file extension which is used to store OLE objects and components. OCX files are typically installed as part of application and could not be launched directly as an executable.

Internally OCX files are DLL files with only difference is that they store ActiveX components. Similarly, to DLL files OCX files are loaded by an application process and mapped into the process address space. After that application can load OLE objects stored in OCX files and use them as part of the application functionality.

Before application can use components inside the OCX file it needs to be registered with Windows OS registry. Most of the times registration happens automatically when application is installed. But sometimes it is necessary to register the OCX file. To do this you can refer to our Regsvr32 utility manual and use this utility to register OCX file.

Sometimes OCX file will not launch because its dependencies are missing. To fix it you can download Dependency Walker tool from and open OCX files in question in it. Dependency Walker will show you what files your OCX file is dependent upon and which of them are missing.

OCX files are typically compiled by developers using developer tools like Visual Studio and languages like C++, Visual Basic, C#, etc. They typically are not distributed separately to end users, but sometimes OCX components are sold as development components by developers to other developers.

Some frequently occurring OCX files are:

  • mscomctl.ocx (Microsoft Common Controls)
  • flash.ocx (Adobe Flash player component)
  • msioff9.ocx (Microsoft System Information Office Extension)
  • comctl32.ocx (Windows Common Control ActiveX Control DLL)
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File Extension Info
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Extension Details
  Dynamic Link Library
Identifying Characters
  Hex: 4D 5A
Opens with
  Text Editor
  Microsoft Visual Studio
  Microsoft Disassembler

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