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cygwin1.dll

Updated: Files Available: 104
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Download and install cygwin1.dll to fix missing or corrupted DLL errors.

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DLL Overview

Last Updated
Jan 1st, 2026
Filename
cygwin1.dll
Company
Red Hat
Product
Cygwin
Description
Cygwin POSIX Emulation DLL
Architecture
x86 (32 bit) x86-64 (64 bit)
Metadata Consensus
104/104 Files 100%
Higher percentages indicate stronger agreement across versions. View available versions or browse repository metadata to compare differences between variants.

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About cygwin1.dll

cygwin1.dll is a DLL file (Dynamic Link Library) used by Windows programs to share code and resources. It allows multiple applications to use the same functions, improving performance and reducing redundancy.

Overview

What Is cygwin1.dll?

cygwin1.dll is the core runtime library of the Cygwin environment — a POSIX-compatible layer that allows Unix/Linux applications to run on Windows. Any program compiled for Cygwin depends on this DLL at startup.

If the file is missing or mismatched, Cygwin-built executables will fail with errors such as:

"cygwin1.dll is missing"
"The procedure entry point ... could not be located in cygwin1.dll"
"Error loading cygwin1.dll"


What Does cygwin1.dll Do?

✔ Provides the POSIX Compatibility Layer

cygwin1.dll implements the Unix-like environment that Cygwin programs expect, including:

  • POSIX system calls
  • Process and signal handling
  • Fork/exec functionality
  • Unix-style file system behavior
  • Pipes, sockets, permissions, and TTY/console handling

It is essentially the Unix kernel interface for Cygwin applications, delivered as a Windows DLL.

✔ Supports Thousands of Cygwin-Compiled Tools

All software built using the Cygwin toolchain relies on this DLL, including:

  • Linux-ported command-line tools
  • Dev tools (GCC, Git, rsync, SSH)
  • Scripting/runtime environments built for Cygwin
  • Custom applications compiled against the Cygwin POSIX layer


Where Is cygwin1.dll Normally Located?

On Windows systems with Cygwin installed, cygwin1.dll resides in:

  • C:/cygwin/bin/cygwin1.dll
  • C:/cygwin64/bin/cygwin1.dll

Some third-party apps bundle their own Cygwin runtime directly inside the program folder.

You should only use the copy that belongs to the version of Cygwin your application was built for.


What Software Uses This DLL?

Common sources of cygwin1.dll include:

  • A full Cygwin installation
  • Applications ported from Linux that ship the Cygwin runtime
  • Developer tools built for Cygwin
  • Internal scripts or automation tools compiled using the Cygwin GCC toolchain

If an .exe is compiled for Cygwin, it must load this DLL.


Why Do cygwin1.dll Errors Occur?

✔ Missing or Not Installed

If Cygwin is not installed (or its /bin folder is missing), dependent programs cannot run.

✔ Version Mismatch

Cygwin is updated frequently. Mixing DLL versions — for example, copying a newer or older cygwin1.dll into a program folder — leads to entry-point errors.

✔ Multiple Copies on the System

Having more than one cygwin1.dll on PATH or in various program folders causes conflicts.

✔ Application Bundled the Wrong Runtime

A program may expect the Cygwin runtime version it was built against; if the bundled DLL is incomplete or corrupted, it will fail.

✔ Antivirus or Security Interference

Security tools sometimes quarantine Cygwin components because they resemble developer toolchains.


How To Fix cygwin1.dll Errors

1. Install or Reinstall Cygwin (Recommended for Most Users)

If the program is meant to run inside a complete Cygwin environment:

  1. Download the official Cygwin installer.
  2. Install Cygwin 32-bit or 64-bit, depending on the program.
  3. Ensure the /bin folder contains cygwin1.dll.
  4. Re-run the application.


2. Use the DLL That Matches the Application’s Build

If the program ships its own cygwin1.dll:

  • Use the DLL included with the application
  • Do not replace it with another version
  • Ensure no other Cygwin runtime on PATH is overriding it


3. Remove Conflicting Copies From PATH

If multiple Cygwin runtimes exist:

  • Remove older or stray Cygwin folders from PATH
  • Ensure the correct cygwin1.dll loads first


4. Reinstall or Update the Application

If only one specific program fails:

  • Reinstall the software so it restores the correct runtime
  • Make sure no other cygwin1.dll is being loaded accidentally


5. Check Antivirus Quarantine

If Cygwin previously worked:

  • Open antivirus logs
  • Restore cygwin1.dll if quarantined
  • Add the Cygwin folder to exclusions if necessary


Summary

cygwin1.dll is the core Cygwin POSIX runtime that enables Unix-like applications to run on Windows. All Cygwin-built executables depend on it.

Errors involving this DLL usually indicate the Cygwin runtime is not installed, the wrong version is being loaded, multiple conflicting copies exist, or the file has been quarantined or corrupted. The most reliable fixes are to install/reinstall Cygwin, ensure the correct DLL version matches the application, and eliminate conflicting or outdated copies.

File information is supported by Human Assisted Artificial Intelligence and should be used as a helpful tool. However, it is important to keep in mind that this information may not be up-to-date or entirely accurate.

Troubleshooting DLL Errors

Most errors involving cygwin1.dll occur because the DLL is missing, corrupted, or outdated. In many cases, reinstalling the related application or replacing the DLL resolves the issue. The steps below cover the most common and reliable ways to fix these errors.

Windows DLL Error Examples

This application has failed to start because cygwin1.dll was not found. Re-installing the application may fix this problem.
cygwin1.dll Not Found.

Fixes and Solutions

The first step in resolving DLL errors is to completely uninstall the affected software and reinstall its latest version. We know this does not always solve the problem, which is why DLLme exists. If reinstalling the application does not help, or if you are unsure which app is causing the error, follow the steps below. These are the most common solutions for fixing cygwin1.dll errors.

  • Repair Windows: Make sure Windows is fully updated, then open Windows Terminal or PowerShell as an administrator (search for “PowerShell” in the Start menu, right-click it, and choose “Run as administrator”). This allows you to repair the Windows component store and run the System File Checker (SFC).

    Repair the Windows component store so SFC can pull clean files:

    DISM /Online /Cleanup-Image /RestoreHealth

    Scan all protected system files and automatically repair problems:

    sfc /scannow
  • Uninstall & Reinstall: On this DLL page, check the Company/Product section to identify the related app, then fully uninstall it. If you plan to continue using it, reinstall the latest version. Be sure to save or back up any important data before uninstalling. Windows or antivirus software may sometimes quarantine DLL files, especially if the DLL is unfamiliar or appears suspicious. Check your antivirus quarantine or logs to determine if this is the cause of your issue.
  • Download the DLL: Download the latest 32-bit or 64-bit version of the DLL directly from our repository using the download button above. Most users will need the 64-bit version, but if you are unsure, or if a 64-bit version is not available, you can install both the 32-bit and 64-bit DLLs. DLLme verifies DLLs that come from our admins, partners, and trusted affiliates. User-uploaded files may be verified later if a trusted source is confirmed.
  • Register the DLL: Most DLL files do not need registration, but some DLLs are COM components and must be registered to work correctly. If registration is required, open Windows Terminal or PowerShell as an administrator.

    Register the DLL (you can also drag the DLL file into the window to automatically fill in its full path):

    regsvr32 "C:\path\to\cygwin1.dll"

    If you are registering a 32-bit DLL on 64-bit Windows, use the 32-bit RegSvr32:

    C:\Windows\SysWOW64\regsvr32 "C:\path\to\cygwin1.dll"

    Or open Windows Terminal/PowerShell in the DLL’s folder and run:

    regsvr32 cygwin1.dll

How to Install cygwin1.dll

To install cygwin1.dll, place the DLL file in the appropriate Windows system folder or in the same folder as the application’s .exe file. If you are not sure which version (32-bit or 64-bit) to use, you can safely install both.

On 64-bit versions of Windows, place 64-bit DLL files in:

C:\Windows\System32\cygwin1.dll

Place 32-bit DLL files in:

C:\Windows\SysWOW64\cygwin1.dll

Or place the DLL file next to the application’s .exe:

C:\path\to\exe\cygwin1.dll

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