Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchPC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11cygstdc++-6.dll is a Cygwin runtime DLL, not a Windows system file. It belongs to GCC’s C++ standard library runtime and is normally installed by Cygwin’s libstdc++6 package.
The safest fix is to repair the Cygwin installation or the third-party application that bundled Cygwin. Do not download a replacement DLL from a random website or copy it into System32.
What cygstdc++-6.dll is
Cygwin-built programs use cygstdc++-6.dll for C++ runtime functions. The file is supplied by the Cygwin package named libstdc++6, described as the GCC C++ runtime library.
Inside Cygwin, the package places the file at:
/usr/bin/cygstdc++-6.dll
On Windows, that normally corresponds to:
<Cygwin-root>bincygstdc++-6.dll
The Cygwin root might be under a path such as C:cygwin64, but the actual location depends on how Cygwin was installed.
Free tools Windows power users keep installed
One-click scans. No signup required.
#1 Best Overall
| Item | Correct identification |
|---|---|
| File | cygstdc++-6.dll |
| Owner | Cygwin libstdc++6 package |
| Source | GCC C++ runtime |
| Windows component | No |
| Usual location | Cygwin’s bin directory |
| Architecture | Must match the Cygwin environment and executable |
| Similar but different file | MinGW libstdc++-6.dll |
Some applications ship a private Cygwin runtime instead of using your main Cygwin installation. In that case, the application’s own installer or repair option is the correct source.
A reported copy may show metadata such as 32-bit, version 0.0.0.0, and a size of 1.47 MB. That metadata does not establish the architecture or version required by every program. The filename alone is not enough to identify whether a particular copy is compatible.
What the error means
You may see any of these messages:
cygstdc++-6.dll was not foundThe program can't start because cygstdc++-6.dll is missing from your computercygstdc++-6.dll: cannot open shared object fileThe procedure entry point ... could not be located- Windows error
0xC0000135
A missing-file message usually means the DLL is absent, damaged, or outside the program’s DLL search path.
An entry-point error is different. It often means the DLL exists but is the wrong version for the executable or another Cygwin library. In that situation, replacing only cygstdc++-6.dll can make the installation less consistent.
Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsFix 1: Repair Cygwin’s libstdc++6 package
This is the most likely fix when the error appears in a Cygwin terminal, Cygwin shell utility, compiler, simulator, or Cygwin-based IDE project.
Close programs using Cygwin
- Close all Cygwin terminals.
- Close the affected application, IDE, compiler, or simulator.
- Stop any service or scheduled task that may be using Cygwin.
- If the installer reports that files are in use, restart Windows and try again before opening the affected program.
Run the matching Cygwin installer
- Start the official Cygwin installer that matches your installation.
- Choose the existing Cygwin root directory when prompted.
- Select a download mirror.
- Continue to the package-selection screen.
- Search for
libstdc++6. - Change the package from
Skipto the available current version. - If it is already selected, choose the installer’s reinstall or version-selection option where available.
- Complete setup and reopen the affected application.
Cygwin provides separate installers for 64-bit and legacy 32-bit installations. The installer names are:
setup-x86_64.exe
setup-x86.exe
Do not install a 64-bit package into a 32-bit Cygwin root or mix two separate Cygwin installations.
For a 64-bit installation, the package can also be selected from a command prompt with:
Quick wins for a faster PC:
Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →setup-x86_64.exe -q -P libstdc++6
For a legacy 32-bit installation, use:
setup-x86.exe -q -P libstdc++6
The command must be run from the directory containing the appropriate installer, or with the full path to the installer.
Confirm that the package owns the file
Open a Cygwin terminal and run:
cygcheck -f /usr/bin/cygstdc++-6.dll
A working installation should identify the owning package as libstdc++6.
You can also search the official Cygwin package repository with:
cygcheck -p cygstdc++-6.dll
If Setup reinstalls the package but the program still fails, continue with the search-path and bundled-application checks below.
Fix 2: Repair the program that bundled Cygwin
Some IDEs, games, utilities, development tools, and commercial applications include their own Cygwin files. They may not use the Cygwin installation in C:cygwin64 at all.
If only one application reports the error:
- Open Settings.
- Select Apps.
- Select Installed apps.
- Find the affected application.
- Open its menu and choose Modify, Repair, or Advanced options, if available.
- Run the application’s repair process.
- If no repair option exists, uninstall it from Installed apps.
- Restart Windows.
- Download the installer from the application developer’s official website.
- Reinstall the application and test it before restoring custom plugins or files.
If the application has a launcher with Verify files, Scan and repair, or similar wording, run that process first.
Installing libstdc++6 into your main Cygwin folder may not repair a program with a private runtime. The correct files must come from the same application installation and must remain internally compatible.
Fix 3: Check the DLL search path
A Cygwin program can work from a Cygwin terminal but fail when launched from File Explorer, a shortcut, or an IDE. The terminal usually sets the environment needed to find Cygwin DLLs. An external launcher may not.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Test from Cygwin
Open the appropriate Cygwin terminal and launch the affected program from there. If it works, the package may be intact and the external launcher is probably using the wrong environment.
Check the application’s environment
For an IDE or development tool:
- Open the IDE’s toolchain or build settings.
- Confirm that it points to the correct Cygwin installation.
- Check that the Cygwin
bindirectory is available to the program. - Save the configuration and restart the IDE.
For a shortcut:
- Right-click the shortcut.
- Select Properties.
- Check Target and Start in.
- Make sure they point to the intended application and installation.
- Avoid launching a 32-bit application with paths belonging to a separate 64-bit Cygwin installation.
Windows searches locations such as the executable’s directory and directories in the process PATH. Do not solve this by copying the DLL to C:WindowsSystem32. Add the correct Cygwin directory only to the affected application’s environment when possible.
Rank #3
Fix 4: Check architecture and mixed installations
Cygwin has separate 64-bit and legacy 32-bit environments. A 32-bit executable cannot use an incompatible 64-bit runtime, and a 64-bit environment should not be mixed with files from a separate 32-bit installation.
To identify the executable’s dependencies, open Cygwin and run:
The Tool Desk
Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →cygcheck /path/to/program.exe
For a Windows-style path, use the path accepted by your Cygwin shell, for example:
cygcheck /cygdrive/c/Program Files/App/app.exe
Look for the Cygwin root and the runtime DLLs being loaded. If the program was installed by a third-party vendor, check that vendor’s documentation for the required architecture.
The repair is to rerun the matching Cygwin installer or reinstall the affected application. Do not replace a 32-bit file with a 64-bit copy because the filename looks identical.
Fix 5: Resolve an entry-point or ABI error
If the message says that a procedure or entry point could not be located, the DLL may exist but be incompatible.
Recommended Free Tools
Common causes include:
- A newer executable with an older Cygwin runtime
- A partial Cygwin update
- Libraries copied from another installation
- A third-party application mixing its private runtime with system Cygwin files
- An incompatible C++ ABI
Repair the entire relevant installation rather than replacing one DLL:
- Close all related programs.
- Run Cygwin Setup.
- Select the existing root directory.
- Update the relevant Cygwin packages, not just
libstdc++6. - Complete Setup.
- Restart the affected program.
For a bundled application, update or reinstall that application instead. A historical program may require the runtime generation shipped with its original installer, so the latest standalone DLL is not automatically correct.
Fix 6: Check antivirus quarantine and accidental deletion
If the file disappeared immediately after a security scan, cleanup operation, or failed update, inspect the security product’s quarantine history.
Rank #4
- Used Book in Good Condition
- Open Windows Security.
- Select Virus & threat protection.
- Select Protection history.
- Review entries associated with the affected application or Cygwin directory.
- Restore a file only when you can verify that it came from the original installation.
- Rerun Cygwin Setup or the application’s repair process afterward.
Do not disable antivirus protection to force a DLL to load. A package repair from the original installer is safer than restoring an unverified standalone file.
Fix 7: Repair Windows components only when Windows has broader problems
cygstdc++-6.dll is not protected Windows system content, so Windows Update, DirectX, .NET, and System32 repairs normally do not restore it.
Use Windows component repair only if other Windows applications also show corruption, protected system files are failing, or Windows itself is behaving abnormally.
Open Command Prompt as administrator:
- Press Start.
- Type
Command Prompt. - Right-click it.
- Select Run as administrator.
- Run:
DISM.exe /Online /Cleanup-Image /RestoreHealth
Wait for it to finish, then run:
sfc /scannow
Restart Windows and test the application. These commands repair Windows images and protected system files. They do not replace the Cygwin libstdc++6 package.
Repeating SFC and DISM without knowing what changed makes this step difficult to evaluate. Outbyte PC Repair can scan for system problems and show what needs attention, while its repair functions require the full version; it is optional, and reinstalling the Cygwin-owning application remains the definitive fix for this DLL.
Fix 8: Update drivers only when there is separate evidence
A graphics, chipset, or storage driver is not the normal owner of cygstdc++-6.dll. Do not install drivers merely because this DLL is missing.
Investigate drivers only if the application also crashes with display, device, or hardware errors:
- Right-click Start.
- Select Device Manager.
- Expand the relevant device category.
- Right-click the device.
- Select Update driver.
- Choose Search automatically for drivers.
- Restart Windows if prompted.
For a graphics or specialized device, use the hardware manufacturer’s official installer when Device Manager finds nothing. Outbyte Driver Updater can scan for outdated drivers and show the results, while installation through the full version is optional; a driver update is not a substitute for repairing the Cygwin package.
What not to do
Do not download the DLL from a random website
Standalone DLL download sites pages can provide malware, the wrong architecture, an incompatible release, or a file missing its dependent libraries. A copied DLL may remove the first error while leaving cygwin1.dll, cyggcc_s-*, or other dependencies broken.
Use the official Cygwin installer or the original application developer’s installer.
Do not copy it into System32
Cygwin normally keeps this file in its own installation tree. A file in C:WindowsSystem32 is suspicious and can cause applications to load an unrelated copy.
Do not use registry cleaners
Runtime DLL loading is not fixed by cleaning registry entries. The relevant problems are usually package integrity, architecture, application environment, or dependency compatibility.
Do not use regsvr32
regsvr32 registers DLLs that expose registration functions such as DllRegisterServer. It is not a generic repair command for runtime libraries, and it normally does not apply to cygstdc++-6.dll.
Do not enable random Windows Features
Installing optional Windows components will not install Cygwin’s GCC runtime. Enable a Windows feature only when a separate application specifically requires it.
FAQ
Is cygstdc++-6.dll part of Windows?
No. It is a Cygwin runtime DLL and does not ship with Windows.
Which package installs it?
Cygwin’s libstdc++6 package, sourced from GCC, installs usr/bin/cygstdc++-6.dll.
Is it the same as MinGW’s libstdc++-6.dll?
No. MinGW uses a different toolchain and a differently named runtime. Do not substitute one for the other.
Why does the file exist but still fail?
A dependent DLL may be missing, the executable may have the wrong architecture, the search path may point to another Cygwin root, or the exported symbols may not match the program’s expected ABI.
Should I install Microsoft Visual C++ Redistributable?
Not as a fix for this file. Microsoft’s C++ runtime and Cygwin’s libstdc++6 are different runtimes.
What if only one program reports the error?
Repair or reinstall that program first. It may contain a private Cygwin runtime that is unrelated to your main Cygwin installation.
What if Cygwin Setup does not solve it?
Run cygcheck against the affected executable, identify the Cygwin root being used, inspect the application’s PATH, and repair the application if it bundles its own runtime. Do not replace individual DLLs until the owning installation is known.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchWindows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallQuick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
