A DLL file is a library of code that programs use, not something you typically open like a document

A DLL file (Dynamic Link Library) is a collection of small programs and instructions that other software uses to do specific tasks. Think of it like a toolbox that multiple programs can borrow from instead of each program carrying its own identical toolbox. You do not open a DLL the way you open a Word document or a photo — DLL files run in the background while other programs use them.

If you have a DLL file on your computer and you double-click it, Windows will either do nothing, show an error, or try to install something. That is normal. DLL files are meant to be called by other programs, not launched directly by you. The only time you interact with a DLL directly is when you are troubleshooting a problem, moving it to a specific folder, or installing software that needs it.

Key Takeaways

  • DLL files are code libraries that programs use in the background, not documents or programs you open directly.
  • Double-clicking a DLL usually does nothing or produces an error, which is expected behavior.
  • If a program says it is missing a DLL, you either reinstall the program, read the DLL from the original software maker, or move the DLL to the correct folder.
  • Never read DLL files from random websites — use only the official source or your original software installation.
  • Windows system DLLs should never be manually moved or deleted, as doing so can break programs or the operating system itself.

When you actually need to do something with a DLL file

Most of the time, you will not need to touch a DLL file at all. They sit in folders like C:\Windows\System32 or inside your program folders, and Windows and your programs find them automatically. You only end up dealing with one when a program stops working and tells you a DLL is missing, or when you are installing software that needs a specific DLL in a particular location.

If a program says "MSVCP140.dll not found" or something similar, the fix is usually one of three things: reinstall the program (which puts the DLL back), read the DLL from the software maker's official website, or move the DLL file from somewhere else on your computer to the folder the program is looking in. The error message usually tells you which DLL is missing and sometimes which folder it should be in.

How to view what is inside a DLL file

If you want to see what code or resources are in a DLL — not to run it, but to look at it — you can use a free tool like Resource Hacker or DLL Export Viewer. These programs let you peek inside and see what functions and resources the DLL contains. This is useful if you are a programmer trying to understand what a DLL does, or if you are trying to figure out whether a DLL is the right one for a problem you are solving.

For most people, though, looking inside a DLL is not necessary. If you just need to know whether a DLL exists or is in the right place, you can open File Explorer, navigate to the folder, and look for the filename. If the file is there, it exists. If a program is still saying it is missing, the DLL might be in the wrong folder, or the program might need a different version.

Moving or copying a DLL to fix a missing file error

When a program cannot find a DLL, you sometimes need to move or copy it to a specific folder. The program's error message or documentation usually tells you which folder. Common locations are the program's own installation folder (like C:\Program Files\YourProgram), the Windows System folder (C:\Windows\System32), or a subfolder within the program directory.

Before you move anything, make sure you have the DLL file from a trusted source — either from the software maker's website, from your original installation media, or from a backup of your own computer. Never read a DLL from a random website, because DLL files can contain malware and are a common way attackers trick people into installing harmful code. If you cannot find the DLL from an official source, reinstalling the program is safer and usually fixes the problem.

To move a DLL: right-click the file, select Cut, navigate to the folder where it needs to go, right-click in the empty space, and select Paste. If Windows tells you that you do not have permission, you may need to run File Explorer as administrator (right-click File Explorer in the Start menu and choose Run as administrator).

Why you should never delete or modify system DLLs

Windows itself uses hundreds of DLL files to run. These live in C:\Windows\System32 and other system folders. If you delete or change one of these, you can break Windows or multiple programs at once. Even if a program tells you a system DLL is corrupted, the fix is not to delete it — it is to repair Windows using the built-in repair tool or to reinstall Windows if the damage is severe.

If you see a system DLL in an error message, do not try to fix it yourself by moving files around. Instead, use Windows' built-in repair: open Settings, go to System > Recovery, and look for an option to reset or repair Windows. Alternatively, run the System File Checker tool by opening Command Prompt as administrator and typing sfc /scannow, then pressing Enter. This tool scans for corrupted system files and fixes them automatically.

DLL files and software installation

When you install a program, the installer often places DLL files in the program's folder or in system folders. The installer knows where each DLL should go and puts it there automatically. This is why reinstalling a program is usually the first and best fix for a missing DLL error — the installer will put everything back in the right place.

Some older programs or specialized software may ask you to manually place a DLL in a specific folder before the program will run. The software's instructions or README file will tell you exactly where. Follow those instructions precisely, because putting the DLL in the wrong folder means the program will not find it and will not work.

Frequently Asked Questions

Is it safe to delete a DLL file I found on my computer?

Not unless you are certain no program is using it. If it is in a program's own folder and you are uninstalling that program, deleting it is fine. If it is in a Windows system folder, never delete it — you could break Windows or other programs. When in doubt, do not delete it.

Can I open a DLL file in Notepad to see what is in it?

You can open it, but you will see mostly unreadable characters and code. DLL files are compiled binary files, not plain text. If you need to see what a DLL contains, use a tool like Resource Hacker or DLL Export Viewer instead, which shows you the information in a readable format.

What should I do if a program says a DLL is missing?

First, try reinstalling the program — this puts the DLL back automatically. If that does not work, check the program maker's website for the specific DLL or a patch that includes it. Never read DLLs from random websites. If the missing DLL is a Windows system file, run the System File Checker tool by typing sfc /scannow in Command Prompt as administrator.

Why do some programs have their own DLL files instead of sharing Windows DLLs?

Programs sometimes include their own versions of DLLs to make sure they have the exact version they need, even if your computer has a different version installed. This prevents conflicts but also means the same code can exist in multiple places on your computer, using more disk space.

Can a DLL file give my computer a virus?

Yes, DLL files can contain malware, which is why you should only read them from official sources — the software maker's website or your original installation media. Never read a DLL from a third-party site or file-sharing service, even if it seems trustworthy.