How to Open DLL File: View Contents, Edit or Fix Missing DLLs

What is a DLL file?

A DLL file is a Dynamic Link Library: a Windows file that holds compiled code, data and resources that one or more programs load while they run. Instead of every program bundling its own copy of common functions, a DLL lets many programs share one copy — less disk space, less memory, and a fix to the library reaches every program that uses it without rebuilding them.

Structurally, a DLL uses exactly the same PE (Portable Executable) format as .exe, .sys and .ocx files: a DOS stub, a COFF file header naming the target CPU, an "optional" header (always present, despite the name) with the entry point and 16 data directories, and a table of sections (.text for code, .data and .rdata for data, .rsrc for resources such as icons). What makes it a DLL rather than an EXE is one bit in the COFF header, IMAGE_FILE_DLL, and an export table listing the functions it offers to other modules.

That's why you never open a DLL file directly: programs do it for you. A DLL also has an import table: the other DLLs it depends on and exactly which functions it calls from each. If one of those is absent when a program starts, you get the familiar "DLL is missing" error. DLLs come in two kinds that need different tools: native DLLs (compiled machine code, usually C or C++) and .NET assemblies (CIL bytecode plus rich metadata, identified by a CLR/COR20 header). The viewer above reads all of this directly.

How to view the contents of a DLL file

To open a DLL file and view its contents, you read its headers and tables (exports, imports, sections, resources), not "open" it like a document. These are the reliable ways to do that, from quickest to most detailed:

dumpbin commands for a quick text dump

On a PC with Visual Studio's C++ build tools, open the Developer Command Prompt and run:

Dependencies is the modern, open-source rewrite of the old Dependency Walker (depends.exe), whose development stopped around 2006. The old tool doesn't understand the API-set DLLs that Windows 10 and 11 use (names like api-ms-win-core-*.dll) and reports them as missing when they aren't, so prefer Dependencies when you're tracking down a real missing dependency. Both tools open DLL files read-only, so they're safe to use on unknown files.

.NET vs native DLL: how to tell and why it matters

Check this before you open a DLL file in any other program. A .NET DLL contains CIL bytecode and full metadata (class, method and field names), so it decompiles back to readable C#. A native DLL contains compiled machine code for one CPU type, so the best you get is assembly or approximate C. The viewer above tells you which one you have on the .NET assembly line of its Overview tab, including the runtime version (for example v4.0.30319) and whether it's IL-only or mixed-mode.

A "mixed-mode" DLL (C++/CLI) contains both, so the viewer shows a CLR header and native code. Note that "IL-only" .NET DLLs marked AnyCPU show x86 as their machine type even though they run as 64-bit in a 64-bit process.

How to decompile or edit a DLL file

You can edit a DLL, but what's realistic depends on its type: resources are easy to change, .NET code is editable, and native code can only be patched at the machine-code level. Always work on a copy — and know that any change breaks the file's digital signature, so signed components may be refused or flagged by antivirus afterwards.

.NET DLLs: decompile back to readable C#

• ILSpy — free, open source (MIT) and cross-platform (Windows, macOS, Linux); open the DLL and browse namespaces, classes and methods as C#.
• JetBrains dotPeek — free decompiler for .dll, .exe and .winmd files that can save a decompiled assembly as a Visual Studio project (.csproj), handy for recovering lost source code.
• dnSpyEx — the community continuation of dnSpy (the original project is no longer developed); it decompiles, debugs and lets you edit methods, classes and metadata, then save a modified assembly.

Decompilers open DLL files read-only, so browsing is harmless; only saving changes alters anything. Obfuscated assemblies (common in commercial software and games) decompile to unreadable names, and many licences forbid decompiling — check before digging into software you don't own.

Native DLLs: disassembly only

Native DLLs contain compiled instructions, not source. Disassemblers and decompilers such as Ghidra (free, published by the NSA), IDA Free or the x64dbg debugger turn them into assembly or approximate C — useful for analysis, but far from the original code. Changing behavior means patching bytes, which is fragile and rarely worth it.

Icons, strings, dialogs and version info

Many DLLs carry Win32 resources. To open a DLL file's icons and text, use Resource Hacker, which (freeware, 32- and 64-bit) lets you add, delete or modify icons, dialogs, menus and strings, then save the file. Visual Studio can also open the resources of a compiled .exe or .dll in its resource editors (this doesn't apply to .NET embedded resources). Never edit a DLL in C:\Windows: Windows Resource Protection guards those files, and a damaged one can stop Windows from starting.

Is it safe to open a DLL file? How to check one

Inspecting a DLL is safe; running or loading it is not. A DLL contains real executable code (or CIL that becomes machine code), so it carries the same risk as an .exe. Malware is very often delivered as a DLL, and DLL side-loading (or DLL hijacking) works by placing a malicious DLL where a trusted program will load it automatically, borrowing that program's trust.

Four checks before you trust a DLL

1. Where did it come from? A DLL installed by a program you trust is normal. One that arrived by email, from a "DLL download" site, or appeared in Downloads on its own deserves suspicion. So does a name that mimics a system file (kerne132.dll) or a "DLL" whose header says it's really an EXE, which the viewer flags.
2. Check the digital signature. Right-click the file → Properties → Digital Signatures tab, select the signer and click Details; it should say "This digital signature is OK". In PowerShell, Get-AuthenticodeSignature "C:\Path\file.dll" returns Valid, NotSigned or HashMismatch (the file was altered after signing) and also checks Windows catalog signatures, which is how many of Windows' own DLLs are signed.
3. Look up its SHA-256 hash. The viewer above computes it and links to VirusTotal's report for that hash, which aggregates dozens of antivirus engines. Only the hash is sent; if VirusTotal has never seen the file, uploading it there shares its contents with security partners, so don't upload confidential in-house DLLs.
4. Scan it locally. Right-click → Scan with Microsoft Defender (on Windows 11, under Show more options).

A missing signature isn't proof of malware — plenty of open-source and older DLLs are unsigned — but a signature that's invalid, or a "Microsoft" DLL that isn't signed by Microsoft, is a strong warning sign.

Fixing "the program can't start because X.dll is missing" errors

A "DLL is missing" or "DLL was not found" error means a program was built to use a library that isn't installed on your PC. You don't need to open a DLL file to fix this; install the package that DLL belongs to, in this order:

1. Read the DLL name in the message and look it up in the package table below — most errors are Visual C++ or DirectX runtimes.
2. Install that official package from Microsoft (or the game/program vendor). For Visual C++ errors install both the x64 and x86 versions.
3. Reinstall or repair the program if the DLL is one of its own files (Steam, Epic and most installers have a repair/verify option).
4. Check your antivirus quarantine if the file existed and vanished (Windows Security → Virus & threat protection → Protection history).
5. For a core Windows DLL (kernel32.dll, user32.dll…), run DISM and SFC.

Which package fixes which missing DLL

The name in the error nearly always tells you where the file officially comes from. Install that package and the DLL lands in the right folder, at the right version, for both 32-bit and 64-bit programs.

Why "latest" matters for Visual C++: Microsoft documents that newer v14 redistributable files work with apps built with older toolsets (2015, 2017…), but not the other way round. If a program still fails after you installed a Visual C++ package years ago, install the current one — an outdated runtime is a common cause of errors like "entry point not found" in MSVCP140.dll.

Repair missing or corrupted Windows system DLLs (SFC and DISM)

If the missing or "not designed to run on Windows" file is a core Windows library — something that ships with Windows itself, such as kernel32.dll, user32.dll or ntdll.dll — Windows can repair it from its own component store. Run these two built-in tools in this order:

1. Open an elevated terminal. Right-click the Start button and choose Terminal (Admin) (Windows 11) or Windows PowerShell (Admin) (Windows 10), then confirm the User Account Control prompt.
2. Repair the component store first: run DISM /Online /Cleanup-Image /RestoreHealth. It downloads clean copies of damaged components from Windows Update and can take a while; it may look stuck at a percentage.
3. Then check the system files: run sfc /scannow. It verifies every protected system file and replaces bad ones with the repaired copies.
4. Restart and try the program again. If SFC reports it couldn't fix some files, the details are in C:\Windows\Logs\CBS\CBS.log.

SFC only covers files that are part of Windows. It will not restore Visual C++, DirectX or game DLLs — for those, use the table above.

Register or unregister a DLL with regsvr32

"Registering" a DLL only applies to COM / ActiveX libraries (including most .ocx files) that export a DllRegisterServer function; registering writes their class IDs into the Windows Registry so other programs can find them. Ordinary DLLs, Visual C++ runtime files and .NET assemblies can't be registered this way, and don't need to be.

1. Open Terminal (Admin) or Command Prompt as administrator.
2. To register: regsvr32 "C:\Path\To\control.dll"
3. To unregister: regsvr32 /u "C:\Path\To\control.dll" (add /s to suppress the message boxes).
4. For a 32-bit DLL on 64-bit Windows, use the 32-bit copy of the tool: C:\Windows\SysWOW64\regsvr32.exe "C:\Path\To\control.dll". The viewer above shows whether a DLL is x86 (32-bit) or x64.

What regsvr32's errors mean

• "The module was loaded but the entry-point DllRegisterServer was not found" — the DLL isn't a COM component (Microsoft's regsvr32 article says it may not be a valid DLL/OCX for registering). Nothing is wrong with it; it simply doesn't need registering. Put it next to the program that uses it instead. Check the viewer's Exports tab: no DllRegisterServer means it can't be registered.
• "The module … failed to load" — wrong path, a 32/64-bit mismatch (try the SysWOW64 copy of regsvr32), or a missing dependency of the DLL itself (check the viewer's Imports tab).
• "…failed with error code 0x80070005" — access denied: the terminal isn't running as administrator.

System32 vs SysWOW64: where 32-bit and 64-bit DLLs go

On 64-bit Windows the folder names are counter-intuitive, and getting them backwards is a common reason a manually copied DLL "doesn't work":

When a 32-bit program asks for System32, Windows silently redirects it to SysWOW64. A 64-bit program can't load a 32-bit DLL (or the reverse) under any circumstances, so check the Architecture line in the viewer's Overview tab: x86 is 32-bit, x64 and ARM64 are 64-bit. On Windows on ARM, x64 and x86 programs run under emulation and still need DLLs matching their own architecture.

Windows' DLL search order is: special locations first (DLL redirection, API sets, side-by-side manifests, DLLs already loaded, and the protected "Known DLLs" list), then the folder the application was loaded from, then the system folders. That's why a DLL placed next to a program's .exe is used by that program — and why attackers plant DLLs there.

Open DLL files on Mac and Linux

You can open DLL files on a Mac or Linux PC to inspect them, but a Windows DLL can't run natively there — it's built for the Windows loader and Windows APIs. What you can still do:

• Inspect it: to open a DLL file on a Mac, Linux PC or phone, use the viewer at the top of this page; it runs in Safari, Chrome or Firefox on any system, including phones, and shows the same header details as on Windows.
• Decompile a .NET DLL: ILSpy's desktop app runs on macOS and Linux as well as Windows.
• Run the Windows program that needs it: Wine is a compatibility layer that runs Windows applications on Linux, macOS and BSD by translating Windows API calls; it loads the program's DLLs as part of that. You can't "run" a DLL on its own, even in Wine.
• Use a .NET library in your own code: a DLL built for modern cross-platform .NET can be referenced from a .NET app on macOS or Linux; one built for .NET Framework or with Windows-only dependencies generally can't.

macOS and Linux have their own shared-library formats (.dylib and .so); renaming a DLL to either doesn't make it work.

Common DLL file problems and how to fix them

"This app can't run on your PC" or error 0xc000007b

Usually an architecture mismatch — a 32-bit (x86) DLL loaded by a 64-bit (x64) program, or the reverse. Check the DLL's Architecture line in the viewer and compare it with the program. Reinstalling both the x86 and x64 Visual C++ Redistributables fixes the most common case.

"The specified module could not be found"

The DLL itself was found, but one of its own dependencies wasn't. Check the viewer's Imports tab for the other DLLs it needs, then confirm each is present (Dependencies shows the whole tree).

"The procedure entry point … could not be located in the dynamic link library"

The DLL exists but is an older or different version that doesn't export the function the program expects. Install the latest version of the runtime it belongs to, or reinstall the program; never mix DLL versions copied from different sources.

"X.dll is either not designed to run on Windows or it contains an error"

This "Bad Image" error (status 0xc000012f) means Windows found the DLL but its contents are invalid — a damaged file, the wrong architecture, or a DLL replaced by a non-PE file. If the named DLL is in C:\Windows, run DISM and SFC; if it belongs to a program or runtime, reinstall that.

The file looks corrupted or won't load in any tool

If no tool can open the DLL file and the viewer reports it's truncated or has no valid PE signature, the download was incomplete or damaged. Get it again from the original source and compare its size and SHA-256 hash.

A DLL keeps disappearing after you restore it

Your antivirus is almost certainly quarantining it. Open Windows Security → Virus & threat protection → Protection history to see what was removed and why. Take that detection seriously — restoring a flagged DLL just to make a program start is exactly how side-loaded malware gets in.

Related file extensions

Sources and technical references

Every program name, command and download on this page was checked against these sources on October 7, 2026:

• PE Format — Microsoft Learn — official PE/COFF specification: headers, sections, imports, exports, the CLR header and the certificate table (whose address is a file offset) that the viewer parses.
• WIN_CERTIFICATE structure — Microsoft Learn — the embedded signature header and certificate types the viewer reports.
• What is a DLL — Microsoft Learn — Microsoft's explanation of DLLs, dependencies and load-time vs run-time linking.
• Dynamic-link library search order — Microsoft Learn — where Windows looks for a DLL, in order.
• Latest supported Visual C++ Redistributable downloads — Microsoft Learn — official x64, x86 and ARM64 v14 (Visual Studio 2017–2026) packages and older runtimes.
• Determining which DLLs to redistribute — Microsoft Learn — Visual C++ runtime DLL names and v14 compatibility rules.
• DirectX End-User Runtime Web Installer — Microsoft Download Center — the official source for d3dx9, XInput 1.3 and XAudio 2.7 files.
• regsvr32 — Microsoft Learn — syntax and the /u, /s, /n and /i switches.
• Regsvr32 error messages and solutions — Microsoft Support — meaning of "failed to load" and "entry-point DllRegisterServer was not found", and the SysWOW64 regsvr32.
• Use the System File Checker tool to repair missing or corrupted system files — Microsoft Support and DISM then SFC order — Microsoft Learn.
• DUMPBIN options — Microsoft Learn — /EXPORTS, /DEPENDENTS, /IMPORTS and /HEADERS.
• Resource files (C++) — Microsoft Learn — editing resources in compiled .exe and .dll files in Visual Studio.
• Get-AuthenticodeSignature — Microsoft Learn — checking embedded and catalog signatures from PowerShell.
• Dependencies — GitHub — open-source rewrite of Dependency Walker with API-set support.
• ILSpy — GitHub, dotPeek — JetBrains and dnSpyEx — GitHub — .NET decompilers and assembly editors.
• Resource Hacker — freeware resource editor for 32- and 64-bit Windows executables and DLLs.
• How VirusTotal works — multi-engine scanning and how submitted files are shared with partners.
• WineHQ — the compatibility layer for running Windows applications on Linux, macOS and BSD.

Frequently asked questions