DLL files are program libraries, not documents you open to read

A DLL file (Dynamic Link Library) is a collection of code that programs use to run. It is not a document like a Word file or a PDF. You do not "open" a DLL the way you open a photo or a spreadsheet. Instead, programs load DLL files automatically when they start up. If a program needs a DLL file to work, it finds and uses it on its own — you do not have to do anything.

The confusion usually starts when your computer shows an error message saying a DLL file is missing or damaged. That error means a program cannot find the code it needs to run. The solution is not to hunt down the DLL file and double-click it. The solution is to fix why the program cannot find what it needs.

If you have a DLL file sitting on your desktop or in a folder and you are wondering what to do with it, the answer depends on where it came from and what program it belongs to. That is what this guide covers.

Key Takeaways

  • DLL files are code libraries that programs use automatically — they are not meant to be opened like regular files.
  • If you see a DLL error message, the problem is usually a missing file or a program installation that went wrong, not a file you need to manually open.
  • Moving or copying a DLL file into a system folder without knowing what you are doing can break other programs or create security problems.
  • The safest approach when you find a stray DLL file is to reinstall the program that uses it, rather than trying to place the file yourself.
  • Downloading DLL files from websites that are not the official program publisher is a common way malware gets onto computers.

When you see a DLL error message

A DLL error usually appears as a pop-up window when you try to open a program. It might say something like "msvcp140.dll not found" or "The program can't start because vcruntime140.dll is missing from your computer." This means the program is looking for a file it needs and cannot find it.

The most common cause is that the program was not installed completely. Reinstalling the program almost always fixes this. Uninstall the program through Windows Settings (Settings > Apps > Apps & features, find the program, click it, and select Uninstall), then read the program again from the official website and install it fresh. The installer will put all the DLL files in the right places.

If the error mentions a Windows system file like "msvcp140.dll" or "vcruntime140.dll", the problem is usually that you are missing a Windows update or a Microsoft runtime library. These are free updates from Microsoft. Search Windows Update in your Settings and run it. If that does not work, you can read the Microsoft Visual C++ Redistributable directly from Microsoft's website — search for "Microsoft Visual C++ Redistributable" and read the version that matches your Windows system (32-bit or 64-bit).

If you downloaded a DLL file from the internet

Downloading DLL files from websites other than the official program publisher is one of the most common ways malware gets onto computers. Even if the website looks legitimate, you cannot know what is actually in the file. Malware creators often disguise malicious code as DLL files and host them on sites that promise to "fix" your computer or provide "missing" files.

If you have already downloaded a DLL file from a third-party website, do not move it into your system folders or try to use it. Delete it. If you need that DLL file to run a program, the safe way to get it is to reinstall the program from its official source — the publisher's website or the Microsoft Store.

The only exception is if a program's official support page or installer specifically tells you to read a particular DLL file from a particular location. Even then, verify the URL is actually the official website before you read anything.

How to check what a DLL file belongs to

If you have a DLL file and want to know what program uses it, right-click the file and select Properties. Look at the Details tab. The "Product name" field usually tells you which program created it. If it says something like "Microsoft Visual C++ Runtime" or "DirectX", it is a system library used by many programs. If it names a specific program, that is the one that needs it.

You can also search the file name online (for example, "d3dx9_43.dll") to find out what it is. Stick to official sources like Microsoft's website or the program publisher's support pages. Avoid downloading from file-sharing sites or "DLL fix" websites.

Once you know what the file belongs to, the next step is to reinstall that program. The installer will place the DLL file in the correct location automatically. Do not try to move or copy the file yourself unless you are following step-by-step instructions from the official program publisher or Microsoft support.

Where DLL files actually live on your computer

Windows stores system DLL files in specific folders, usually "C:\Windows\System32" or "C:\Windows\SysWOW64" (for 32-bit programs on a 64-bit system). Individual programs also store their own DLL files in their program folders, usually under "C:\Program Files" or "C:\Program Files (x86)".

You should not manually move or copy files into these system folders. If you put a DLL file in the wrong place, or if you put a malicious DLL file in a system folder, you can break Windows or other programs. Windows has security protections that prevent you from editing these folders without administrator permission for exactly this reason.

If a program needs a DLL file and it is not there, the program's installer should put it there. If the installer does not, then something went wrong with the installation, and you should reinstall the program rather than trying to fix it manually.

DLL files and program compatibility

Sometimes a DLL error happens when you upgrade Windows or move a program to a different computer. This usually means the program was built for an older version of Windows or needs a library that is not installed on the new system.

The fix is almost always to reinstall the program on the new system. Do not try to copy DLL files from the old computer. Programs are designed to install their own dependencies in the right way for the system they are running on. Copying files between computers usually creates more problems than it solves.

If you are trying to run very old software on a new version of Windows, you may need to use Compatibility Mode. Right-click the program's shortcut or .exe file, select Properties, go to the Compatibility tab, and try running it in Compatibility Mode for an older Windows version. This tells Windows to emulate an older system environment, which sometimes helps old programs find the libraries they need.

Frequently Asked Questions

Can I just double-click a DLL file to open it?

You can, but nothing useful will happen. Windows will either show an error or try to run the code inside it, which is not what you want. DLL files are meant to be used by programs, not opened directly. If you need to see what is inside a DLL file, use a file viewer tool designed for that purpose, but this is rarely necessary for normal computer use.

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

Only if you are sure no program uses it. If you delete a DLL file that a program needs, that program will stop working. If you found a DLL file in a suspicious location or downloaded it from the internet, deleting it is the right move. If it is in a Windows system folder or a program's installation folder, leave it alone unless you are uninstalling that program.

What should I do if I keep getting the same DLL error?

Try reinstalling the program first. If that does not work, check Windows Update to make sure your system is current. If the error mentions a Microsoft runtime library, read and install the latest Microsoft Visual C++ Redistributable from Microsoft's website. If none of that works, search the exact error message on the program publisher's support page — they may have a specific fix for that error.

Why do some websites offer to read DLL files for me?

These sites make money by getting you to read files, and many of them bundle malware with the DLL files they offer. Even if the DLL file itself is real, the read site may have infected it. The legitimate way to get a DLL file is to reinstall the program that needs it from the official publisher.

Can I move a DLL file from one program's folder to another?

Not safely. Even if two programs use a DLL file with the same name, they may need different versions of it. Moving files between program folders can break both programs. Let each program manage its own files through its installer. If two programs need the same library, they should both install their own copy.