.DLL File Extension
Dynamic Link Library
| Developer | Microsoft |
| Popularity |
4.2 | 6744 Votes |
| Category | System Files |
| Format | Binary |
What is a DLL file?
A DLL file is a compiled library containing a set of procedures and/or drivers referenced and executed by a Windows program. It allows multiple programs to access shared functions through common libraries. DLL files are "dynamically linked" into a program at runtime, meaning they are only loaded when needed.
Many DLL files are provided with the Windows operating system, while others are included with Windows programs. They enable various program functions, such as communication with external devices and reading and writing files.
When a program needs to perform a certain function stored in a DLL file, it calls on the DLL file containing the code for that function. The file may store code for one application or multiple applications and be linked together with other DLL files, so when a program calls one DLL file, it also calls the linked DLL files.
Common DLL Filenames
user32.dll - Contains instructions for graphical elements such as dialog boxes and windows. If you try to open a program and Windows reports you're missing user32.dll, you can re-install the program, update Windows, use a system restore point, or repair your copy of Windows to fix the issue.
shell32.dll - Contains Windows shell API functions. If you try to open a program and Windows reports you're missing shell32.dll, you can re-install the program, update Windows, use a system restore point, or repair your copy of Windows to fix the issue.
msvcrt.dll - Contains standard C library functions. If you're missing msvcrt.dll, you can install the Microsoft Visual C++ 2015 Redistributable Package to install it and related DLLs.
mfc42u.dll - A Microsoft Foundation Class (MFC) library required by some Windows programs. If you're missing mfc42u.dll, you can use a system restore point or repair your copy of Windows to fix the issue.
mfc80u.dll - An MFC library required by some Windows programs created with Visual C++ 2005. If you're missing mfc80u.dll, you can install the Microsoft Visual C++ 2005 Redistributable Package to install it and related DLLs.
mfc90u.dll - An MFC library required by some Windows programs created with Visual C++ 2008. If you're missing mfc90u.dll, you can install the Microsoft Visual C++ 2008 Redistributable Package to install it and related DLLs.
mfc100u.dll - An MFC library required by some Windows programs created with Visual C++ 2010. If you're missing mfc100u.dll, you can install the Microsoft Visual C++ 2010 Redistributable Package to install it and related DLLs.
How to open a DLL file
In general, you should not manually open DLL files since they are meant to be referenced and executed by Windows programs. In fact, opening and modifying a DLL file may cause errors within the program referencing the file and cause it to stop working altogether.
If a DLL file becomes corrupt or is missing, you may need to reinstall the program or download and install a new version of the DLL. Be sure to verify the download source's legitimacy since DLL files can be used to distribute malware.
While it is not advised, you can decompile and modify DLL files with various applications. Some options include Microsoft Visual Studio, JetBrains dotPeek, Redgate .NET Reflector, and Resource Hacker.
Warning
DLL files are typically legitimate libraries used by Windows applications, but they can also be used to distribute and execute malware attacks on victims' computers. To protect against malware attacks, never install a DLL file you downloaded from the Internet unless you trust the file's source.
Programs that open or reference DLL files
What is a DLL file?
A DLL file is a webpage generated dynamically when accessed by a user. It may incorporate server-side scripts, such as Perl or VB scripts that generate the webpage's HTML.
Webpages with DLL file extensions are typically hosted on Microsoft IIS web servers. The DLL extension must be mapped to the correct scripting engine on the server for the page to be processed correctly.