Question 1

A program says a DLL is missing. Should I download it?

Accepted Answer

No - not on its own, and not from "DLL download" websites, whose files are often the wrong version, outdated or infected. A missing DLL belongs to something: reinstall the program that shows the error, or install the package the DLL comes from, from its maker. Files named msvcp140.dll, vcruntime140.dll or mfc140u.dll come with the Microsoft Visual C++ Redistributable; d3dx9_43.dll and xinput1_3.dll with the DirectX End-User Runtime. Dropping a copy of the DLL here shows which program or package it belongs to.

Question 2

How can I tell if a DLL or EXE is safe?

Accepted Answer

Start with who made it and whether it is signed: a file from Microsoft, Adobe or another large company is signed by that company, and the page checks that the signature matches the file. An unsigned file that claims to be from one of them, or a signed file that has changed since it was signed, is a warning sign. Being signed is not a guarantee on its own, and an unsigned file is not necessarily harmful - many small programs are unsigned - so for anything doubtful, also scan it with your antivirus before running it.

Question 3

Is this DLL 32-bit or 64-bit?

Accepted Answer

The page says, under its name: x86 for 32-bit, x64 for 64-bit Intel and AMD, or ARM64. A 64-bit program can only load 64-bit DLLs and a 32-bit one only 32-bit DLLs, which is behind many "not a valid Win32 application" and "bad image" errors: on 64-bit Windows, 32-bit DLLs belong in C:\Windows\SysWOW64 and 64-bit ones in C:\Windows\System32.

Question 4

Can it show the code inside, or edit it?

Accepted Answer

No. A DLL's code is machine code, which needs a disassembler or, for .NET files, a decompiler such as ILSpy to read. This page shows everything the file says about itself, which answers what it is and who made it, and changes nothing.

What is this DLL or EXE file? Find out without running it

Report a problem