What is afd?

Afd.sys is a Windows driver. A driver is a small software program that allows your computer to communicate with hardware or connected devices. This means that a driver has direct access to the internals of the operating system, hardware etc. The free file information forum can help you determine if afd.sys is a Windows system file or if it belongs to an application that you can trust.

Run a free scan to check for afd drivers in need of updating

Afd.sys file information

The process known as Ancillary Function Driver for WinSock or AFD belongs to software Microsoft Windows Operating System or Ancillary Function Driver for Winsock or Ancilliary Function Driver for Winsock or AFD Networking Support Environment by Microsoft (

Description: The original afd.sys is an important part of Windows and rarely causes problems. Afd.sys is located in the C:\Windows\System32\drivers folder. Known file sizes on Windows 10/8/7/XP are 138,496 bytes (67% of all occurrences), 138,368 bytes and 4 more variants. 
The driver can be started or stopped from Services in the Control Panel or by other programs. Afd.sys is a Windows core system file. The program has no visible window. The afd.sys file is a trustworthy file from Microsoft. afd.sys appears to be a compressed file. Therefore the technical security rating is 0% dangerous, however you should also read the user reviews.

Recommended: Identify afd.sys related errors

Important: Some malware disguises itself as afd.sys, particularly when not located in the C:\Windows\System32\drivers folder. Therefore, you should check the afd.sys process on your PC to see if it is a threat. We recommend Security Task Manager for verifying your computer's security. This was one of the Top Download Picks of The Washington Post and PC World.


User Comments

Adress F61E67FC
My MP4 device couldn't connect to my computer
obviously it works in kernel mode, and its a TDI Client.
  Himanshu Pareek   (further information)
keeps making a blue screen show on my laptop running vista
its bloody important
  manglah   (further information)
knowledge base
unless it is new from MS, i do not trust it as an experienced computer user having not seen it before am vary.
It's a system kernel driver, aka "AFD Networking Support Environment" and is part of the Windows TCP/IP stack, supporting socket operations. Some versions of Windows apparently exhibit a memory leak with this driver (link: and, while Windows diagnostics reports that it does accept the "stop"'s probably best to understand its role first. See "link for more info's", i.e., "How To: Harden the TCP/IP Stack." My advice? Don't mess with it, unless you know *exactly* what you're doing.
  Kirk M. Schafer   (further information)
This is one of three dependencies for the DHCP service. If the file goes missing, DHCP will fail to start. Some infections may corrupt the file. Errors like RPC server is unavailable when trying to renew the systems IP address via DHCP. You can simply replace the adf.sys file from another system running the same OS and Service Pack.
If you are running a Network Using DHCP, you need this Driver to do it. The DHCP Service on a Domain Controller Depends on AFD
it works with ie, i remove it and my ie was not working
  Donavon Simonette  
It crashes windows 7 RC1
network driver
AFD.sys is a Windows-integrated file. Windows will crash without it.   (further information)
Required component for WS2_32 operation
Its needed for proper DHCP and TCP/IP operation
David's advice worked for me; used the copy in winnt\system32\dllcache. Don't know for certain, but the original might've been damaged by a Trojan from a web site.
Virus/trojan trapped by AVG software but the "fix" left me with a corrupt winsock interface. Tried everything; netsh, winsockfix, etc. No good. Per this thread, ran a binary compare (fc.exe) and found the afd.sys files differed between system and dllcache. Restored the system32 version and problems solved. Thanks!
Threat W/32...
my virus protection said it was a root kit and everything choked.I ran a scan got new driver now everything is flying fast
It is used for winsock and a dummy driver in its place crashes even if you don't use winsock.
  Robert Arkenin  
Original name of afd.sys was, "Another Driver".
  MS Techie  
"keeps making a blue screen show on my laptop running vista" me too

Rating chart

Summary: Average user rating of afd.sys: based on 23 votes with 23 user comments. 14 users think afd.sys is essential for Windows or an installed application. 3 users think it's probably harmless. One user thinks it's neither essential nor dangerous. 2 users suspect danger. 3 users think afd.sys is dangerous and recommend removing it. 5 users don't grade afd.sys ("not sure about it").

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Best practices for resolving afd issues

A clean and tidy computer is the key requirement for avoiding problems with afd. This means running a scan for malware, cleaning your hard drive using cleanmgr and sfc /scannow, uninstalling programs that you no longer need, checking for Autostart programs (using msconfig) and enabling Windows' Automatic Update. Always remember to perform periodic backups, or at least to set restore points.

Should you experience an actual problem, try to recall the last thing you did, or the last thing you installed before the problem appeared for the first time. Use the resmon command to identify the processes that are causing your problem. Even for serious problems, rather than reinstalling Windows, you are better off repairing of your installation or, for Windows 8 and later versions, executing the DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.

To help you analyze the afd.sys process on your computer, the following programs have proven to be helpful: Security Task Manager displays all running Windows tasks, including embedded hidden processes, such as keyboard and browser monitoring or Autostart entries. A unique security risk rating indicates the likelihood of the process being potential spyware, malware or a Trojan. Malwarebytes Anti-Malware detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.

Other processes

afd.sys [all]