What is slui.exe?

The .exe extension on a filename indicates an executable file. Executable files may, in some cases, harm your computer. Therefore, please read below to decide for yourself whether the slui.exe on your computer is a Trojan that you should remove, or whether it is a file belonging to the Windows operating system or to a trusted application.

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Slui.exe file information

Windows Task Manager with slui
Slui.exe process in Windows Task Manager

The process known as Windows Activation Client belongs to software Microsoft Windows Operating System by Microsoft (

Description: Slui.exe is an important part of Windows, but often causes problems. The slui.exe file is located in the C:\Windows\System32 folder. Known file sizes on Windows 10/8/7/XP are 325,632 bytes (85% of all occurrences), 312,320 bytes or 349,184 bytes. 
It is a Windows core system file. Slui.exe is a Microsoft signed file. The program is not visible. Therefore the technical security rating is 7% dangerous, however you should also read the user reviews.

Recommended: Identify slui.exe related errors

Important: Some malware disguises itself as slui.exe, particularly when not located in the C:\Windows\System32 folder. Therefore, you should check the slui.exe 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

It executes a window that allows the user to change the operating system key. It is run from the command prompt. The correct syntax in win 7 or 8 is "slui.exe 3"
The file is not needed for the operating system to work properly. It handles the legitimacy of the Windows licence and provides a nag and/or timed reboot if your version of Windows is not genuine.
If unable to activate online, you can always run "slui.exe 4" to open the activate by phone option. This is an automated process in which your computer provides a long number that you input to Microsoft via phone. Once verified, Microsoft will give another long number to input on the activation screen to activate windows. While it is not "essential" to Windows, slui may be needed to activate Windows following installation.
  Joseph Brooks  
The version that came up on my desktop was not signed by Microsoft therefore I stopped it. If Microsoft want to run such program in the process of installing Visual Studio it needs to sign them.
  David Millsom  
Its the activation client for Windows and is required if you are running a genuine system.
Just had Microsoft rework my system after a new NIC was installed, the tech ran slui 4 and 2hours later, my pc is back, though, some customisations are off (eg: desktop background) ... I consider it safe.
if running a secure pc, this file could be hacked to not allow license verrification then Microsoft forces a user to connect online in order to activate the license and hackers may then breach the once secure system. Microsoft then said that I could not be helped despite owning a legitimate copy and that I needed to purchase a new full license if I refused to connect. This is despite having all original hardware so that it knew it was the same PC and not some attempt to bootleg copies of their OS. Hackers commonly use "legitimate" companies to get you to break security protocols for them and unfortunately the companies are all too willing to help them with this goal.
  Paul Ikeda  

Rating chart

Summary: Average user rating of slui.exe: based on 8 votes with 7 user comments. 3 users think slui.exe is essential for Windows or an installed application. 2 users think it's neither essential nor dangerous. One user suspects danger. 2 users think slui.exe is dangerous and recommend removing it.

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Best practices for resolving slui issues

A clean and tidy computer is the key requirement for avoiding problems with slui. This means running a scan for malware, cleaning your hard drive using 1cleanmgr and 2sfc /scannow, 3uninstalling programs that you no longer need, checking for Autostart programs (using 4msconfig) and enabling Windows' 5Automatic 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 6resmon 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 7DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.

To help you analyze the slui.exe process on your computer, the following programs have proven to be helpful: ASecurity 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. BMalwarebytes Anti-Malware detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.

Other processes

slui.exe [all]