mono-2.0-bdwgc.dll Errors: Restore the Correct Unity Runtime

Short answer

mono-2.0-bdwgc.dll is a private Unity runtime file, not a Windows system DLL. If Windows says mono-2.0-bdwgc.dll is missing, was not found, or could not be loaded, repair the game or Unity installation that owns it before trying Windows-wide DLL fixes.

The file normally belongs inside a Unity game, Unity Editor installation, or Unity-based tool. It is commonly stored under a path similar to:

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<Game>\MonoBleedingEdge\EmbedRuntime\mono-2.0-bdwgc.dll
<Game>\<Game>_Data\MonoBleedingEdge\EmbedRuntime\mono-2.0-bdwgc.dll
<Unity>\Editor\Data\MonoBleedingEdge\EmbedRuntime\mono-2.0-bdwgc.dll

The exact location depends on the Unity release, whether the file belongs to a game or Editor, the build layout, and whether the program uses a 32-bit or 64-bit runtime.

The safest repair is to verify the affected game through its launcher. If that does not restore the file, reinstall the game from its official store or publisher. For a Unity project, reinstall the exact Unity Editor version and Windows build-support module used by that project.

Do not download a replacement DLL from a random DLL website, copy it into System32, or run regsvr32. Those actions can introduce the wrong build, wrong architecture, malware, or a misleading temporary fix.

What mono-2.0-bdwgc.dll is

Unity uses a fork of the open-source Mono project for its Mono scripting backend. Unity embeds that runtime into Editors and Windows players rather than installing it as a normal shared Windows component.

The bdwgc part refers to the Boehm-Demers-Weiser garbage collector used by the runtime. In practical terms, the file is part of the managed-code environment that a Mono-based Unity game needs while starting and running.

Older Unity releases could contain both Mono and MonoBleedingEdge runtimes. Unity 2019.3 and later use MonoBleedingEdge as the Mono variant. This is why the surrounding folder often includes MonoBleedingEdge\EmbedRuntime.

This file is used by:

• Unity-built Windows games that use the Mono scripting backend
• Unity Editor installations
• Unity-based development tools
• Some modded or extended Unity game installations

Not every Unity game contains this file. Some Unity games use IL2CPP instead of Mono, which has a different native scripting backend. If a game was built with IL2CPP, installing a Mono DLL is not the correct solution.

There is no universal mono-2.0-bdwgc.dll that works for every game. The correct file is tied to the exact Unity release, game build, architecture, and development or non-development configuration. A file with the same name from another Unity game may be incompatible.

Some file-information listings show a 32-bit record with version 0.0.0.0 and a size of about 3.43 MB. That does not establish a universal version, size, architecture, or hash for every copy. Different Unity releases can ship materially different builds.

Fix 1: Verify the game files through its launcher

Time needed: 5 to 30 minutes, depending on the game size and drive speed.

This is the most likely fix for a missing or corrupt Unity runtime. It restores files from the game’s own manifest instead of guessing which DLL version belongs there.

Steam

1. Restart Steam.
2. Open Library.
3. Right-click the affected game.
4. Select Properties.
5. Select Installed Files.
6. Select Verify integrity of game files.
7. Wait for Steam to finish.
8. Start the game from Steam rather than from an old desktop shortcut.
9. Test the same action that previously produced the error.

Steam may report that some files failed to validate because local configuration files are expected to differ. The important question is whether the Unity runtime was reacquired and whether the game now starts.

If the error remains, restart Steam and repeat the verification once. If the same file is repeatedly reacquired or repeatedly disappears, continue with the antivirus, permissions, disk, and mod checks below.

Epic Games Store

1. Open the Epic Games Launcher.
2. Select Library.
3. Find the affected game.
4. Select the three-dot menu beside the game.
5. Select Manage.
6. Select Verify.
7. Wait for the process to complete.
8. Launch the game from Epic Games.

Other launchers

Look for an option named Verify, Repair, Scan and repair, Validate, or Check files. It is usually available from the game’s menu, properties page, or installation-management screen.

If the game was manually copied between computers, moved from another drive, heavily modified, or installed from an unofficial package, launcher verification may not have a complete source for the original files. In that case, reinstall it from the original publisher or store.

How to tell whether this worked

The repair succeeded if:

• The game starts normally.
• The missing-file dialog no longer appears.
• The launcher no longer reports a damaged installation.
• The original MonoBleedingEdge folder and executable-to-data-folder relationship are restored.

Do not copy mono-2.0-bdwgc.dll from another Unity game. Matching the filename is not enough.

Fix 2: Check Windows Security quarantine

Time needed: 5 to 10 minutes.

Antivirus software can quarantine or remove a file that was present when the game previously worked. This is especially worth checking if the error began after an update, mod installation, or security scan.

1. Open the Start menu.
2. Type Windows Security.
3. Open Windows Security.
4. Select Virus & threat protection.
5. Select Protection history.
6. Review recent actions involving the game folder or mono-2.0-bdwgc.dll.
7. Open the relevant detection to inspect its path and action.
8. Restore the file only if the game came from a legitimate store or publisher and the path clearly belongs to that installation.
9. After restoring it, run the launcher’s file verification again.
10. Start the game and test it.

Microsoft documents Protection History and its restore options in Windows Security Protection History.

Do not blindly restore a DLL from a cracked, modified, or unknown game package. An antivirus detection may indicate that the installation itself is unsafe. Remove the questionable software and perform a full security scan instead.

If the file disappears again after verification, inspect the antivirus action carefully. Repeated removal can also indicate that a mod, unofficial launcher, or altered executable is changing the installation.

Fix 3: Reinstall the game or the exact Unity Editor version

Time needed: 20 minutes to several hours, depending on the download size.

Use this fix when verification does not restore the file, the installation is incomplete, or the game folder was manually rearranged.

Reinstall a game

1. Back up save files if the game stores them outside the installation folder.
2. Disable or remove third-party mods temporarily.
3. Uninstall the game through its launcher.
4. Restart Windows.
5. Install the game again from the same official store or publisher.
6. Allow the installation to finish without pausing or moving the game folder.
7. Run the launcher’s verification step after installation.
8. Start the unmodified game before reinstalling mods.

Do not restore a previously modified MonoBleedingEdge folder over the fresh installation. Test the clean installation first.

Repair a Unity Editor installation

For a Unity project, the runtime must match the Editor version used to create or build the project.

1. Open Unity Hub.
2. Select Installs.
3. Find the required Editor version.
4. Open its options menu.
5. Choose Add modules or the equivalent module-management option.
6. Ensure the required Windows build-support module is installed.
7. If the Editor installation is damaged, remove that Editor installation through Unity Hub.
8. Install the same Editor version again.
9. Open the project and test the build or Editor.

Use the exact Editor release required by the project. Installing a newer Unity release may change the runtime and does not guarantee compatibility with an existing project.

How to tell whether this worked

A successful reinstall restores the executable, its matching _Data folder, and the appropriate MonoBleedingEdge runtime structure. The game or Editor should start without a Windows loader dialog.

If the error appears only after adding a mod, the clean installation is probably healthy. Reintroduce modifications one at a time and stop when the failure returns.

Fix 4: Repair the Microsoft Visual C++ Redistributable

Time needed: 10 to 20 minutes, including a restart.

A DLL can be visibly present while Windows still reports that it cannot load. In that situation, the named file may be present but one of its dependent runtime components may be missing.

Unity has documented Windows Mono-player failures on fresh Windows installations caused by a missing Visual C++ runtime.

Install the package that matches the game architecture:

• 32-bit game: install the x86 package
• 64-bit game: install the x64 package
• 64-bit Windows does not eliminate the need for x86 when the game itself is 32-bit

Use Microsoft’s official installers:

• Visual C++ Redistributable x64
• Visual C++ Redistributable x86

Microsoft’s package documentation is available in Latest Supported Visual C++ Redistributable Downloads.

1. Close the game and its launcher.
2. Download the required x86 or x64 package from Microsoft.
3. Run the installer.
4. Accept the license terms.
5. If Repair appears, select Repair.
6. If only Install appears, complete the installation.
7. Restart Windows.
8. Launch the game again.

If the game includes a _CommonRedist or Redist folder, run its bundled prerequisite installer first. Some older games require a particular legacy runtime in addition to the current package.

This repair replaces neither mono-2.0-bdwgc.dll nor the Unity installation. It addresses the case where the Unity DLL is present but Windows cannot load a dependency.

Manually hunting through multiple Visual C++ packages is tedious, particularly after a fresh Windows installation. Outbyte PC Repair can scan for missing or damaged Windows components and show what needs attention; its repair functions require the full version, and reinstalling the affected game remains the definitive fix when the missing file belongs to that game.

Fix 5: Check the game folder layout and launch permissions

Time needed: 10 to 20 minutes.

Unity players expect the executable, its data folder, and runtime folders to remain in a particular relationship. Moving only the executable, nesting the game one folder too deeply, or using a mod launcher that changes the working directory can cause a loader failure.

A typical layout may look similar to:

GameFolder\
    Game.exe
    Game_Data\
        MonoBleedingEdge\
            EmbedRuntime\
                mono-2.0-bdwgc.dll

Another Unity generation may place the runtime directly under the game folder:

GameFolder\
    Game.exe
    MonoBleedingEdge\
        EmbedRuntime\
            mono-2.0-bdwgc.dll

The exact layout varies. Do not create folders just to match an example.

To inspect the installation:

1. Open the game launcher.
2. Open the game’s properties or management menu.
3. Select Browse local files, Open installation folder, or the equivalent option.
4. Confirm that the game executable and its _Data folder belong to the same installation.
5. Search within that folder for mono-2.0-bdwgc.dll.
6. Confirm that it is inside a Unity runtime directory rather than a random downloads folder.
7. Remove temporary duplicate copies outside the official installation only if you know they are leftovers and are not save files or mod files.
8. Start the game through the launcher.

If the game was moved manually, use the launcher’s own move or library-management feature. Do not move only the executable or only the _Data directory.

Try administrator access only as a test

Running as administrator can help when permissions prevent the game from reading its own runtime, but it does not repair a missing DLL.

1. Right-click the game executable.
2. Select Properties.
3. Open the Compatibility tab.
4. Select Run this program as an administrator.
5. Select Apply, then OK.
6. Launch the game once.

If this works, the underlying issue may be folder permissions, security software, or an installation location with restricted access. Avoid leaving permanent administrator compatibility enabled unless the game requires it.

A better long-term repair is to reinstall or move the game through its launcher to a normal library folder, then verify the files.

Fix 6: Disable mods and third-party launchers

Time needed: 10 to 30 minutes.

A broken mod can overwrite Unity runtime files, alter the startup command, add an incompatible native plugin, or create a second nested game directory.

1. Close the game and launcher.
2. Disable the mod manager profile.
3. Move custom mod files to a temporary folder outside the game directory.
4. Do not delete save files unless you have confirmed where they are stored.
5. Run the launcher’s file verification.
6. Start the unmodified game.
7. If it works, add mods back individually.
8. Test after each change.

If the game works without mods but fails with one specific mod, contact that mod’s maintainer or remove it. Do not replace the Mono runtime to compensate for a mod that was built for another game version.

A mod launcher can also cause a misleading “module not found” error if it starts the executable from the wrong working directory. Test the normal launcher executable directly after restoring the original files.

Fix 7: Update Windows and repair protected Windows components

Time needed: 15 to 45 minutes, excluding a large Windows update.

This is a secondary repair because mono-2.0-bdwgc.dll normally belongs to the application directory, not to a protected Windows system folder. Windows repair commands normally do not restore a private Unity runtime.

Install Windows updates

1. Open Start.
2. Select Settings.
3. Select Windows Update.
4. Select Check for updates.
5. Install available updates.
6. Restart Windows when prompted.
7. Return to Windows Update and check again.
8. Test the game.

Microsoft’s procedure is described in Install Windows updates.

Run DISM

1. Open Start.
2. Type Command Prompt.
3. Right-click Command Prompt.
4. Select Run as administrator.
5. Select Yes at the User Account Control prompt.
6. Run:

DISM /Online /Cleanup-Image /RestoreHealth

1. Wait for the command to finish.
2. Restart Windows if DISM requests it.

Run System File Checker

Open an elevated Command Prompt again and run:

sfc /scannow

Wait until the scan reaches 100 percent, then restart Windows and test the game.

Microsoft recommends repairing the Windows image with DISM before running SFC. The documented procedure is in Use the System File Checker tool to repair missing or corrupted system files.

The result matters:

• No integrity violations: Windows protected files were not the problem.
• Corrupt files repaired: restart and test the game.
• Some files could not be repaired: run DISM again, restart, and repeat SFC once.
• The game still reports the same Unity DLL: return to launcher verification or reinstall the game.

SFC and DISM are not substitutes for restoring a missing game file.

Repeating SFC and DISM without knowing what changed can waste time. Outbyte PC Repair can show missing or damaged Windows components in a scan; repair functions require the full version, and it should not be treated as a replacement for repairing the game installation.

Fix 8: Update or reinstall drivers only when the evidence points there

Time needed: 10 to 30 minutes.

A driver update is not a normal fix for a genuinely missing mono-2.0-bdwgc.dll. It becomes relevant when the game starts but crashes, Event Viewer also names a graphics or audio driver, the crash began immediately after a driver change, or the crash occurs during rendering, sound playback, or a scene transition.

Check Device Manager

1. Open Start.
2. Type Device Manager.
3. Open Device Manager.
4. Expand Display adapters.
5. Expand Sound, video and game controllers.
6. Look for a warning icon or an affected device.
7. Right-click the device.
8. Select Properties.
9. Open the Driver tab.
10. Note the provider, date, and version.
11. Use Update Driver only when a newer driver is available from the hardware manufacturer or Windows Update.

For a graphics driver problem, download the driver from the GPU manufacturer’s official support page. For an audio problem, use the computer or motherboard manufacturer’s support page.

Roll back a recently changed driver

If the crash began immediately after a driver update:

1. Open Device Manager.
2. Right-click the affected device.
3. Select Properties.
4. Open the Driver tab.
5. Select Roll Back Driver if available.
6. Restart Windows.
7. Test the game.

Do not uninstall an important device driver without having a replacement source and a recovery plan. A driver reinstall cannot restore the Unity Mono DLL.

Driver version hunting is especially difficult when several devices show stale or incompatible packages. Outbyte Driver Updater can scan for outdated drivers and identify what needs attention; driver installation through the full version is optional, and it does not replace repairing the game files when the Unity runtime is missing.

Fix 9: Identify whether the error is a load failure or a crash

Time needed: 10 to 20 minutes.

The same filename can appear in two very different situations.

Loader failure

These messages usually indicate that Windows or Unity could not load the runtime:

The program can't start because mono-2.0-bdwgc.dll is missing from your computer.

The code execution cannot proceed because mono-2.0-bdwgc.dll was not found.

Unable to load mono library from <path>\MonoBleedingEdge\EmbedRuntime\mono-2.0-bdwgc.dll

Start with file verification, antivirus history, installation layout, architecture, and Visual C++ dependencies.

Bad-image or incompatible-module failure

This message indicates a different class of problem:

mono-2.0-bdwgc.dll is either not designed to run on Windows
or it contains an error.

Common possibilities include:

• The file is corrupt.
• The file belongs to another Unity build.
• The architecture does not match the executable.
• A dependent module is missing or incompatible.
• A mod replaced the original file.
• The installation was only partially copied.

Restore the exact file through the launcher or reinstall the exact program. Do not solve a bad-image error by downloading the same filename from another source.

Crash report or faulting module

A crash may say:

mono-2.0-bdwgc.dll caused an Access Violation (0xc0000005)

This means the DLL was the reported faulting module at the moment of failure. It does not prove that the DLL itself is defective.

The underlying cause may be:

• Managed game code
• A native plugin
• A mod conflict
• Memory corruption
• A Unity engine bug
• A graphics or audio interaction
• A damaged game installation
• A driver problem

If the game reaches the menu and crashes during a save, scene transition, mod action, or particular visual effect, treat the filename as a crash location rather than proof of a missing runtime.

Fix 10: Read the Unity player log

Time needed: 5 to 15 minutes.

The player log can distinguish a missing file from a dependency problem or a later crash.

For current Unity Windows players, check:

%USERPROFILE%\AppData\LocalLow\<CompanyName>\<ProductName>\Player.log

Older Unity versions may use:

output_log.txt

near the game’s data folder.

To open the current log location:

1. Press Windows key + R.
2. Enter:

%USERPROFILE%\AppData\LocalLow

1. Press Enter.
2. Open the company folder.
3. Open the product folder.
4. Open Player.log with Notepad.

Search the file for:

mono-2.0-bdwgc.dll

Also inspect the lines immediately before the failure. Look for:

• The full path Unity attempted to load
• A missing dependency
• A graphics or audio initialization failure
• A mod or plugin name
• An access-denied message
• The Unity version
• The scripting backend
• Repeated startup errors

Save a copy of the log before reinstalling because reinstalling or deleting configuration files may change the evidence.

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Check 32-bit and 64-bit compatibility

Time needed: 5 to 15 minutes.

Unity Windows builds can have separate 32-bit and 64-bit runtime variants. A 32-bit DLL cannot be substituted for a 64-bit runtime, and a 64-bit DLL cannot be loaded by a 32-bit executable.

The architecture of Windows is not the same as the architecture of the game. A 32-bit game can run on 64-bit Windows and still needs its x86 dependencies.

To determine whether the error belongs to a 32-bit game:

1. Open the game’s installation folder.
2. Check the launcher or publisher documentation for the supported architecture.
3. Look at the game’s executable properties if the publisher identifies the build.
4. Check whether the launcher offers separate 32-bit and 64-bit versions.
5. Install x86 Visual C++ support for a 32-bit game even when Windows is 64-bit.

Do not infer the correct Mono DLL from a file size shown on a download page. The correct source is the exact game build or Unity Editor installation.

What not to do

Do not use random DLL download websites

A downloaded copy can be:

• The wrong Unity release
• The wrong architecture
• Incompatible with the game build
• Modified or infected
• Missing its own dependencies
• A misleading replacement for the real installation repair

There is no single official universal download package for this filename. The safe source is the game launcher, the official publisher, or the exact Unity Editor installation used by the project.

Do not copy it to System32 or SysWOW64

mono-2.0-bdwgc.dll is normally application-local. Copying it into a Windows system directory can cause unrelated programs to load an incompatible runtime and makes future troubleshooting harder.

Windows normally searches the application directory as part of DLL loading. Keeping the game’s private runtime beside the game preserves the intended version relationship.

Do not run regsvr32

Do not run:

regsvr32 mono-2.0-bdwgc.dll

regsvr32 is intended for DLLs that expose a COM registration entry point such as DllRegisterServer. A Unity embedded Mono runtime is loaded by the Unity player; it is not normally registered as a COM component. Registration will not repair a missing dependency, wrong architecture, corrupt file, or broken game layout.

Microsoft describes the registration entry point in Implementing DllRegisterServer.

Do not install standard Mono as a substitute

A standard Mono Windows installation is not guaranteed to repair Unity’s embedded MonoBleedingEdge runtime. Unity’s fork, release, build configuration, and directory layout matter.

Likely causes and the matching repair

Symptom	Likely cause	Correct next step
File is absent from the game folder	Failed update, incomplete install, deletion, or quarantine	Verify files, then reinstall if necessary
File exists but Unity says it cannot load it	Missing dependency, architecture mismatch, or permissions	Repair Visual C++, check architecture and layout
Error began after installing a mod	Mod replaced files or changed startup paths	Disable mods and verify the installation
Error returns after every verification	Antivirus, disk, permissions, or launcher conflict	Check Protection History, disk health, and third-party launchers
Game reaches a menu and then crashes	Managed code, plugin, mod, driver, memory, or engine issue	Read Player.log, test a clean installation, inspect crash data
Event Viewer names the DLL as faulting module	Crash location, not proof of a bad DLL	Investigate logs, mods, plugins, and drivers
Error appears after copying the game manually	Broken executable, _Data, or runtime relationship	Use the launcher’s move or reinstall function
Only a 32-bit game fails on 64-bit Windows	Missing x86 dependency	Install the x86 Visual C++ Redistributable
SFC reports no problems but the game still fails	Application-local Unity files are damaged	Verify or reinstall the game

If verification and reinstalling do not help

Work through these checks in order:

1. Confirm the game is unmodified.
2. Check Windows Security Protection History.
3. Check whether the file is recreated and then removed.
4. Confirm the executable and _Data folder are from the same installation.
5. Repair both relevant Visual C++ architectures if the game’s architecture is uncertain.
6. Check Player.log.
7. Test with overlays, injectors, and third-party launchers disabled.
8. Check for graphics or audio driver errors.
9. Test the game from a different library folder or drive if disk errors are suspected.
10. Contact the game developer with the exact error, game version, Unity version if shown, Player.log, and any crash dump.

If the game fails only with a particular save, scene, mod, or plugin, replacing mono-2.0-bdwgc.dll is unlikely to solve it.

If the game fails before displaying anything and the file is absent, the game installation remains the primary suspect. If the file is present and the game crashes later, treat the DLL name as evidence about where the crash surfaced, not as a diagnosis by itself.

FAQ

Is mono-2.0-bdwgc.dll part of Windows?

No. It is normally a private Unity runtime file stored with the game, Unity Editor, or Unity-based tool that installed it. It should not normally be placed in C:\Windows\System32 or C:\Windows\SysWOW64.

Where should the file be located?

Common locations include:

<Game>\MonoBleedingEdge\EmbedRuntime\
<Game>\<Game>_Data\MonoBleedingEdge\EmbedRuntime\
<Unity>\Editor\Data\MonoBleedingEdge\EmbedRuntime\

The correct path varies by Unity release and build layout.

Can I copy the file from another Unity game?

No. The same filename can represent different Unity builds, architectures, and runtime configurations. Restore it from the affected game or exact Unity installation.

Does every Unity game use this file?

No. Some Unity games use Mono, while others use IL2CPP. IL2CPP builds use a different native scripting backend.

Why does Windows say the file is missing when I can see it?

The file may be present but unusable because a dependency is missing, the architecture is wrong, the file is corrupt, permissions prevent access, or the executable is using a different installation path. Repair Visual C++, verify the folder layout, and inspect the Unity log.

Do I need the x86 or x64 Visual C++ package?

Match the game, not merely Windows. A 32-bit game needs the x86 package even on 64-bit Windows. A 64-bit game needs x64 support.

Should I use regsvr32?

No. This runtime is loaded by Unity and is not normally a COM DLL that should be registered.

Should I run SFC and DISM?

You can use them as secondary Windows repairs, especially if other Windows components are also failing. They normally do not restore a missing application-local Unity DLL. Verify or reinstall the game first.

What if Event Viewer says mono-2.0-bdwgc.dll caused an access violation?

That identifies the reported faulting module, not necessarily the original cause. Check Player.log, disable mods and native plugins, test the clean game, and investigate graphics, audio, memory, and driver issues.

Is the file malware?

The filename alone does not establish whether a file is safe or malicious. Verify its path and provenance. A copy restored by an official game launcher is materially different from an unexplained DLL downloaded from an unknown source.

Will reinstalling standard Mono fix the game?

Not necessarily. Unity embeds its own MonoBleedingEdge runtime, so the dependable repair is restoring the exact game or Unity Editor installation.

What is the final repair if all other steps fail?

Remove third-party modifications, back up saves, reinstall the game from its official source, and test the clean installation before restoring mods. For a Unity project, reinstall the exact Editor version and Windows build-support module required by the project.

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