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“ The program can’t start because assimp-vc140-mt.dll is missing from your computer.” You may also see “assimp-vc140-mt.dll was not found,” “The specified module could not be found,” or “assimp-vc140-mt.dll could not be loaded.”
assimp-vc140-mt.dll is an application file from Assimp, a library used by games, graphics programs, Unreal projects, and other software to import 3D model data. It is not a Windows system file, and the safest repair is to restore it through the application that installed it.
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The 60-second fix
- Identify the game or program shown in the error or the shortcut you tried to open.
- Repair, verify, update, or reinstall that application from its official installer or launcher.
- Check Windows Security’s quarantine history before copying any replacement file.
- Do not download the DLL from a random DLL website.
- If you built the program yourself, deploy the matching Assimp build beside the executable that actually runs.
For a Steam game, open Steam, select Library, right-click the game, choose Properties, select Installed Files, and choose Verify integrity of game files. When verification finishes, launch the game again. If the file is restored and the program starts, the application installation was incomplete or corrupted.
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Assimp is an open-source, cross-platform library for importing 3D models. A program that supports formats such as those used by 3D assets may load Assimp when it starts or when it opens a model.
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The filename gives useful build information:
assimpidentifies the Assimp library.vc140indicates the Microsoft Visual C++ 14.0 toolset associated with Visual Studio 2015.mtidentifies the multithreaded runtime configuration.- A Debug build commonly uses
assimp-vc140-mtd.dllinstead.
The name does not identify one universal release, file size, hash, or publisher. Different applications can package different Assimp builds, so a copy that works for one program may be wrong for another.
This file normally sits beside the application executable or in the program’s build or staging output. It does not belong in C:WindowsSystem32 or C:WindowsSysWOW64.
Why the error appears
The most common causes are:
- The application installation is incomplete or damaged.
- Antivirus software quarantined the DLL.
- An update or uninstall removed the file.
- The DLL was placed in the wrong output directory.
- A 32-bit program received a 64-bit DLL, or the reverse.
- A Debug program is missing the Debug
-mtdvariant. - Assimp is present, but one of its dependencies is missing.
- The installed DLL belongs to a different Assimp build.
The file may be bundled with many unrelated programs. Its presence alone does not tell you which application owns it.
Fix 1: Repair or reinstall the owning application
This is the correct first repair for most users.
Use the application’s repair option
- Open Settings.
- Select Apps, then Installed apps.
- Find the affected program.
- Select the three-dot menu beside it.
- Choose Advanced options, if available.
- Select Repair.
- Start the program again.
If there is no Repair option, open the program’s own launcher and look for Verify, Repair, Scan and repair, or Check files.
For a desktop installer that provides no repair option:
- Download the installer again from the application developer or official store.
- Close the affected program.
- Run the installer.
- Choose Repair if offered.
- Otherwise uninstall the application, restart Windows, and install it again from the official source.
Do not manually remove the DLL before reinstalling. Let the installer place the file in the directory expected by the executable.
A successful repair restores the file and allows the application to start normally. If the same error returns immediately, continue with the quarantine check rather than repeatedly reinstalling.
Fix 2: Check Windows Security quarantine
Antivirus software can remove a legitimate application DLL after an update or a scan. It can also correctly block a modified or malicious replacement, so restore a file only when you trust its source.
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- Open Windows Security from the Start menu.
- Select Virus & threat protection.
- Select Protection history.
- Look for an event involving the affected application or
assimp-vc140-mt.dll. - Expand the event and review its location and action.
- If the file came from the official application installation, use the available Restore or Allow on device action.
- Repair or verify the application afterward.
If the entry identifies an unfamiliar location, a temporary folder, or an unofficial DLL, do not restore it. Remove the file, run a scan, and reinstall the application from its official source.
If the file disappears again after restoration, check whether the application updater, cleanup utility, permissions, or antivirus policy is removing it. Repeated disappearance is evidence of an installation or security problem, not a reason to copy the DLL into a system folder.
Fix 3: Check the application’s actual output directory
A DLL can exist on the computer and still be invisible to the program that needs it. Windows normally searches locations associated with the running executable, not every folder on the drive.
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Find the shortcut for the affected application, right-click it, and choose Open file location. Look for the executable and check whether assimp-vc140-mt.dll is beside it.
For a project, check the directory containing the executable you launch, not merely the Visual Studio solution directory. An Unreal project may need the DLL in its staged or packaged BinariesWin64 output rather than in the source tree.
If you are the developer:
- Confirm which executable is failing.
- Copy the vendor-supplied Assimp DLL beside that executable through the project’s deployment or post-build rule.
- Rebuild or restage the application.
- Launch the newly produced executable, not an older copy elsewhere.
- Remove stale output directories if the build system is mixing configurations.
Do not rename another DLL to assimp-vc140-mt.dll. The filename alone does not make its exports, architecture, or dependencies compatible.
Fix 4: Match 32-bit and 64-bit architecture
A 32-bit process cannot load a 64-bit Assimp DLL, and a 64-bit process cannot load a 32-bit DLL.
For a packaged application, reinstall or verify the application so its own installer supplies the correct build. Do not choose a replacement based only on whether Windows is 64-bit. A 64-bit version of Windows can run many 32-bit applications, which still require 32-bit libraries.
For a project, confirm all three items:
- the application architecture;
- the Assimp library architecture;
- the directory from which the executable is launched.
Use the 32-bit Assimp output with a 32-bit executable and the 64-bit output with a 64-bit executable. After correcting the architecture, clean the project, rebuild it, and run the new output.
Fix 5: Check Debug versus Release
The requested filename is the Release-style assimp-vc140-mt.dll. A Debug build commonly expects assimp-vc140-mtd.dll.
In Visual Studio:
- Open the project.
- Check the toolbar’s Solution Configuration.
- Select Debug or Release intentionally.
- Check Solution Platform and select the correct x86 or x64 target.
- Clean the solution.
- Rebuild it.
- Run the executable from that configuration’s output folder.
Do not copy the Release DLL into a Debug output folder simply to satisfy the filename. Debug and Release builds can use different runtime settings and dependencies. Deploy the matching Assimp variant or change the project configuration so the expected file and the built application agree.
Fix 6: Distinguish Assimp from the Microsoft runtime
The Microsoft Visual C++ Redistributable does not install assimp-vc140-mt.dll.
Install or repair the official Visual C++ Redistributable only when the error also names a Microsoft runtime file such as:
VCRUNTIME140.dllMSVCP140.dllapi-ms-win-crt-*.dll
Use Microsoft’s latest supported Visual C++ Redistributable downloads. Choose x86 for a 32-bit application and x64 for a 64-bit application. On 64-bit Windows, a 32-bit program still needs the x86 package.
The current v14 Redistributable is designed to support applications built with several Visual Studio generations, but it still will not provide the Assimp DLL. Installing Visual Studio itself is usually unnecessary for someone who only wants to run a packaged application.
If the error names only assimp-vc140-mt.dll, repair the owning application first.
Fix 7: Diagnose “specified module” and “not designed to run” errors
“The specified module could not be found” does not always mean the named Assimp file is absent. The file may exist while one of its own dependencies is missing.
Likewise, “not designed to run on Windows” or “contains an error” can indicate:
- a damaged DLL;
- the wrong architecture;
- a Debug/Release mismatch;
- an incompatible Assimp build;
- a missing dependency;
- a program loading a different copy than the one you repaired.
Check the file path beside the running executable, then repair the application from its official source. Developers should inspect the executable’s dependency chain with their normal build and diagnostic tools, rebuild Assimp with the same architecture, compiler toolset, runtime mode, and configuration, and redeploy all required files together.
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Fix 8: Update graphics drivers only when there is a wider graphics problem
A graphics driver normally does not restore an application-owned Assimp DLL. Consider a driver repair only when the same program also reports graphics initialization failures, rendering crashes, or device errors.
To check drivers manually:
- Right-click Start and select Device Manager.
- Expand Display adapters.
- Right-click the graphics device.
- Select Update driver.
- Choose Search automatically for drivers.
- Restart Windows if a driver is installed.
For a clean repair, obtain the driver from the computer or graphics-card manufacturer. Do not expect this step to fix an isolated assimp-vc140-mt.dll error.
If you prefer not to hunt through hardware pages and compare driver versions manually, Outbyte Driver Updater can scan and show outdated drivers; its repair or driver installation is handled by the full version. Reinstalling the affected game or application remains the definitive fix when that program owns the DLL.
Fix 9: Use DISM and SFC only for broader Windows corruption
System File Checker and DISM repair protected Windows components. They do not normally restore a third-party Assimp DLL, so use them when several unrelated Windows components or applications are failing.
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Command Prompt. - Right-click Command Prompt.
- Choose Run as administrator.
- Run:
DISM.exe /Online /Cleanup-Image /RestoreHealth
- Wait for it to complete.
- Then run:
sfc /scannow
- Restart Windows and test the application.
Microsoft documents this DISM and SFC repair procedure.
If manually checking component health and repeating repairs is becoming guesswork, Outbyte PC Repair can scan for reported Windows issues; the free scan shows what it finds, while repair is handled by the full version. For an application-owned Assimp file, repairing or reinstalling the owning program remains the definitive fix.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What not to do
- Do not download
assimp-vc140-mt.dllfrom a random DLL repository. - Do not copy it into
System32orSysWOW64. - Do not rename another DLL.
- Do not run
regsvr32for this file. Assimp is a normal application library, not an ActiveX or COM component that needs registration. - Do not install Visual Studio solely because the filename contains
vc140. - Do not remove older Visual C++ Redistributables just because a newer package is installed.
- Do not use Windows Features to add Assimp. It is not a Windows optional component.
- Do not assume SFC can replace an application-owned DLL.
Unofficial downloads can contain malware, the wrong architecture, a different build, or incompatible dependencies. The safe sources are the application’s official installer, its official launcher, the developer’s own project artifacts, or a verified build produced by your team.
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FAQ
Is assimp-vc140-mt.dll part of Windows?
No. It is an Assimp library distributed with a third-party application, game, or project.
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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Do I need Visual Studio 2015?
Usually no. vc140 describes the toolset used to build the DLL. It does not normally mean the end user must install Visual Studio 2015.
Will the Visual C++ Redistributable restore the file?
No. It can provide Microsoft runtime files required by the application, but it does not contain Assimp.
Where should the DLL be located?
Normally beside the executable that loads it or in the application’s actual build or staging output. The correct location depends on the application’s deployment layout.
Why does the file exist but Windows still report it as missing?
A dependency of the DLL may be missing, or the program may be loading another copy. Architecture, Debug/Release configuration, corruption, and incompatible builds can produce the same message.
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1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteHow do I know which application installed it?
The filename is not enough to identify an owner. Start with the shortcut, launcher, game, or project that displays the error. Repair that application rather than repairing the DLL globally.
When should I use SFC or DISM?
Use them when multiple unrelated Windows components are failing or there is evidence of broader Windows corruption. For an isolated Assimp error, repair the owning application first.
What information should I provide if the problem continues?
Record the exact error text, application or game name, Windows architecture, executable architecture, full DLL path, whether the file exists, whether Windows Security quarantined it, and whether another missing DLL is named. That information distinguishes an incomplete installation from a dependency or deployment problem.
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