If you open the Windows Task Manager, you may see a process csrss.exe. This is Client Server Runtime file, and it is a Windows operating system file located in the System32 folder. So what is this csrss.exe? How do you know if it is a virus or not? Why does it consume high CPU on Windows 11/10 at times and what do you do about this?
What is Client Server Runtime or csrss.exe process in Windows?
The Client Server Runtime process has a long history. Before 1996, the process managed the entire graphical subsystem; today, it is restricted to a few critical tasks, such as shutting down Windows and starting the console.
CSRSS stands for Client/Server Runtime Subsystem, and it must run at all times. Earlier, Client Server Runtime launched Command Prompt; however, since Windows 7, the process is limited to launching conhost.exe, which in turn launches Command Prompt.
Can we terminate the csrss.exe process?
The Client Server Runtime process has limited functionality for Windows systems as of present, however, that limited functionality is critical. You cannot kill the process and doing so forcibly would make the system unusable. It may shut down the computer automatically.
However, the process has no reason to over-utilize system resources and since it runs in the background, it shouldn’t bother you for any reason.
Is csrss.exe a virus or trojan?
The original Client Server Runtime process is located in the C:\Windows\System32 directory. 
If the file is not located in the intended location, a virus or malware may be using the same name. Please run an antivirus to perform a full system scan.
To confirm, right-click the file once you open the folder, locate it and check its Properties.
If the csrss.exe process causes high CPU usage, it could be a virus.
Do I need csrss.exe on my computer?
Yes, you do need csrss.exe on your computer as it is a Windows OS file. You cannot kill the process and doing so forcibly would make the system unusable. It may shut down the computer automatically.
Why do I have two csrss.exe files running in Task Manager?
It is normal to see two csrss.exe processes running in the Task Manager even when you are the only person logged in. But to be sure, you can check their file locations and run an antivirus scan as well. The image above is from my single-user PC and you can see 2 processes there.
Hope this clarifies the matter.
Want to know about these processes, files or file types?
Windows.edb files | WAB.exe | ctfmon.exe | Nvxdsync.exe | Svchost.exe | RuntimeBroker.exe | TrustedInstaller.exe | DLL or OCX files. | StorDiag.exe | MOM.exe | Host Process for Windows Tasks | ApplicationFrameHost.exe | ShellExperienceHost.exe | winlogon.exe | atieclxx.exe | Conhost.exe.
