Open DLL File Extension – What it is and How to Open .dll Files

File Type Dynamic Link Library Aka’ DLL
Who Developed it Microsoft
Category System Files
File Format Binary
Identifying Character Hex: 4D 5A
MIME Type application/octet-stream

.dll file

A DLL (Dynamic Link Library) file is an executable Windows file that allow programs to obtain additional libraries & functionality without having to have them built – in to the program itself. Mostly DLL files work in background and loaded only when they needed. You rarely have to face and deal with a DLL file. DLL contains a set of method / procedure that are used and executed by a windows program used as “Application Extension”. A DLL files can be shared between different multiple windows program. MS Windows. Many DLL files are built in with Windows Operating System, while others are included with windows application programs. Dll file allows multiple application to access shared functions via same common libraries. Windows Operation System uses Dynamic Link Library file to keep executable codes for various windows components like Networking, graphical engine, printing, communication with external hardware devices and reading or writing file.

You can find most of the DLL files at C:\Windows\System32 folder and in same manner Windows applications keep their DLL files at C:\Program Files or C:\Program Files (x86) in corresponding folders. When You move your mouse courser to any application and double click it, clicked Windows application start to find its DLL file in related folder and store them in to memeory.DLL File is the most frequent occurring file on your laptop or computer.

Playing with DLL file isn’t advised. Editing and deleting the contents of a DLL may make you in trouble cause errors within the application that corresponding the file. If a windows application seeks to fetch a DLL File that already been missing or corrupted, that program will no longer open until you reinstall the program or manually download and install a new version of the DLL file.

How to check whether the file is DLL or Not

  • At first you have in your mind, how to check if a specific file is DLL or Not?
  • Don’t worry just follow the steps given below.
  • Open DLL file with text editor ex: Notepad or a hex editor.
  • Check if first two characters are MZ in the opened file and rest are binary symbols.
  • Extension of opened file is DLL.

Caution: Please don’t download Dynamic Link Library / DLL files from untrusted websites. It may contain viruses and affect your computer system.

How to open DLL File

Method 1 Register a New DLL File

DLL files are vital part of Windows Programming. If you want to copy a manually downloaded DLL file into a folder for an application program to use. First you have to register same DLL file to Windows registry before it can be used. To do same just follow the following steps: –

  • Open the Microsoft DOS known as Command Prompt (cmd). To open Command Prompt just press Windows Key + R and type cmd and hit enter or You can find Command prompt in Start Menu too.
  • Now navigate to the New DLL File location.
  • If you are use Windows 7 or higher version of Windows like Windows 8 or Windows 10, open the file folder containing the new DLL file, press and hold the shift key and right click on the folder containing the DLL files and from dropdown menu select “Open command window here” or “Open PowerShell Window here”. Command Prompt / PowerShell window will open directly to the same folder.
  • Now you need to type regsvr32 dllfilename.dll and hit enter. This command will add DLL file to windows registry.
  • To remove a DLL file from Windows Registry just Type regsvr32 -u dllfilename.dll.

You can also use various applications to view and edit DLL files. These applications are basically known as Decompiler. A “Decompiler” is a program that helps you to see the source code that was used to built a file or program. A decompiler is used to see the code that makes a DLL file work in readable form. If you ever opened a DLL file without decompiler (Opening it with text editor like notepad) will resulted you unreadable characters.

Method to open a DLL file using Visual Studio

  • Open Start Menu
  • Search for Visual Studio Tool and hit enter key
  • Navigate to above folder.
  • Click on the icon “Visual Studio Command Prompt” for Visual Studio 2010 or If you are using Visual Studio 2013 press on “Developer Command Prompt”.
  • Now type “ILDASM.EXE” and hit enter key.
  • Drag and drop the dllfilename.dll to window.
  • Click “File the navigate to New” and add required .DLL file.
  • .DLL file will appear.
  • Press these files and you can easily watch the contents of files.

How to decompile a DLL File

Many decompilers are available to download and use. I suggest dotPeeK decompiler one of the most popular free decompiler. You can download and install dotPeek decompiler from web easily. I hope you have downloaded and install dotPeek now simply click on File now click on open and browse DLL file you wanna decompile. Now you are able to explore the contents of DLL file without harming your system.

DLL file is the collection of nodes / module of code that work together. Using “Assembly Explorer” you can expand each node and watch subnodes if the file contains. The code for the selected node will appear in right frame of dotPeek software window, in that frame you can review the code. dotPeek software is able to download additional libraries automatically in order to view the original source code it they needed. If you are not able to understand piece of code what they are doing. Move and place your cursor to the piece of code and press Ctrl + Q simultaneously, the Quick Documentation window will appear. There you can follow the hyperlinks to learn more about pieces of code you are examining.

How to edit a DLL File

If you want to want to edit or manipulate a DLL file or built a DLL file on your own. You can directly export it from dotPeek software to Visual Studio. The exported code will be in C#. Here is steps to export

  • Right click on the DLL file in Assembly Explorer.
  • Select “Export to Project” from opened drop down menu.
  • Your project is opened on Visual Studio immediately. Now you have complete control building / editing of DLL file.

List of popular windows and mac apps can be used to open DLL Files

  1. Microsoft Visual Studio
  2. Microsoft Disassembler
  3. Microsoft Azure
  4. Eclipse
  5. Apache NetBeans
  6. Visual Studio Code
  7. Microsoft Visual FoxPro


Various DLL file extension

  1. SYS File- Contains method and procedure to operate Operation System Code.
  2. COM File- Contains method and procedure to operate the DOS style Code.
  3. SCR File- Contains method and procedure to operate some codes for screensavers.
  4. EXE File- Contains method and procedure to operate codes for applications.
  5. DRV File- Contains method and procedure to operate codes for the drivers.