iisfcgi.dll - Analyze and How to Fix Errors

★★★★☆ Verified File (27.08.2026) The file was obtained from the pack Windows 7

⚠️ Important Notice: Optimize your IIS with iisfcgi.dll for enhanced CGI handling. Improve server performance and application compatibility. Manually replacing system libraries can brick future Windows updates or cause critical system failures.

Architecture:	64-bit (x64)	Compatible with only 64-bit Windows
Creation date	20.11.2010 15:02:03
File version	7.5.7601.17514
Antivirus scan	✅ Clean	No viruses detected.
Digital signature	🟡 Not signed	Signature missing. The file may have been modified.
Hash Integrity	✅ MD5: Verified	File Hash protection is missing.
File size	85.5 kb.	87552 bytes.

Hashes:

MD5: 06d4732e974e06c57fd6a2d5f54a75d5 ✅
SHA-1: a4cded796263bc726958f0b8bc1fdcf1273632a2
SHA-256: 7b93a1f6bd98e91591f89e24d46161d9db11f5e7511afcaf0b111e3ab2dce0a1
SHA-512: 9168f642f3ad432fba036539e2f76b8f7360820e6b87c3efba8a169bbb84111b483f2a792365350d28037b2780c82d55c1b6fb7c8bf73a0a562a565ad9b6f422

✅ This file is compatible with 64-bit Windows and ❌ will not work on a 32-bit operating system.

File Description: iisfcgi.dll

iisfcgi.dll is a critical dynamic link library file belonging to Microsoft Internet Information Services (IIS). It serves as the FastCGI (Fast Common Gateway Interface) Handler Module.

Purpose

This file enables IIS to pass web requests to external application frameworks. It is primarily used to host non-Microsoft scripting languages like PHP, Python, or Ruby on a Windows Server, allowing them to run efficiently by keeping application processes alive between requests.

Standard File Location

On a standard Windows Server installation with IIS enabled, the file is located in the global IIS library directory:

C:\Windows\System32\inetsrv\iisfcgi.dll

Note: If you are running a 64-bit Windows OS, the 32-bit compatibility version may also exist in C:\Windows\SysWOW64\inetsrv\, though IIS primarily relies on the System32 path for the core worker processes.

How to Fix iisfcgi.dll Errors (Without Downloading)

If you are experiencing crashes, "file not found" errors, or HTTP 500.x FastCGI errors pointing to iisfcgi.dll, do not download the DLL from third-party websites. This is unsafe and rarely fixes the root cause. Instead, use these built-in Windows repair methods.

Method 1: Re-Register the IIS CGI/FastCGI Feature

Most iisfcgi.dll errors occur because the FastCGI module was corrupted or disabled during a Windows update. Re-enabling the feature forces Windows to restore the original file from its secure component store.

For Windows Server:

Open Server Manager.
Click Manage > Remove Roles and Features.
Advance to Server Roles > expand Web Server (IIS) > expand Web Server > expand Application Development.
Uncheck CGI. Click Next and finish the removal.
Reboot the server.
Open Server Manager again, go to Add Roles and Features, and re-check CGI to cleanly reinstall it.

For Windows 10 / 11:

Press Win + R, type optionalfeatures.exe, and press Enter.
Scroll down to Internet Information Services > World Wide Web Services > Application Development Features.
Uncheck CGI and click OK to uninstall it.
Restart your computer.
Reopen the same menu, check CGI, and click OK to restore the file.

Method 2: Run System File Checker (SFC)

If the actual file inside System32 is missing or corrupted, the Windows Component Store can automatically repair it.

Right-click the Start Menu and select Terminal (Admin) or Command Prompt (Admin).
Type the following command and press Enter:
```
sfc /scannow
```
Wait for the verification to reach 100%. If it finds corrupt files, Windows will automatically replace iisfcgi.dll with a clean copy.

Method 3: Fix PHP/Python Handler Mapping Mismatches

If the error is an HTTP 500 error inside your web browser rather than a Windows crash, the DLL file itself is fine, but IIS is misconfigured.

Open the IIS Manager (inetmgr).
Click on your server name or specific website in the left panel.
Double-click on Handler Mappings in the center menu.
Look for your PHP or FastCGI mapping (e.g., PHP via FastCGI).
Ensure the executable path points correctly to your php-cgi.exe (or Python equivalent), and not directly to the iisfcgi.dll file. The DLL handles the process routing, but it must know where the actual language interpreter lives.

Method 4: Restart the IIS Service

Locked files or memory leaks can cause the DLL to fail intermittently. A clean reset fixes temporary environment issues.

Open Command Prompt (Admin).
Run the command:
```
iisreset
```

📊 Diagnostics Tool: Verify Your `iisfcgi.dll` File

Worried that the file on your PC has been modified by malware? Drop it into the form below. Our script will verify its file size, cryptographic hash (MD5/SHA-1), and check for a valid Microsoft digital signature.

Connected files:
msvcrt.dll
├── KERNEL32.dll
├── IISUTIL.dll
├── ADVAPI32.dll
├── WS2 32.dll
├── RPCRT4.dll
└── ntdll.dll
Other versions:
️ iisfcgi.dll 7.5.7601.17514 32-bit (x86) | ️ iisfcgi.dll other
Similar files:
️iisfcgi.dll.mui