What is mscorsvw.exe?

The genuine mscorsvw.exe file is a software component of Microsoft .NET Framework Optimization Service by Microsoft Corporation.
Microsoft's .NET Framework Optimization Service (mscorsvw.exe) runs in the background to make the Native Code Generator (NGEN.exe) convert .NET Framework library routines to machine code so that applications written for .NET run faster. Unlike many Windows services it does not always run when Windows boots, only when a given version of the .NET framework is first installed on a computer or is changed by Windows Update, (usually on "Patch Tuesday", the second Tuesday of each month). If multiple versions of .NET exist on a system in "C:\Windows\Microsoft.NET\Framework", such as "…\ v2.0.50727" and "…\ v4.0.30319", each will have its own "ngen.exe" and "mscorsvw.exe" executable files. Originally, (since .NET Framework 1.0 before 2005), through Win7, "mscorsvw.exe" ran "ngen.exe" to compile the entire .NET library to machine code, which caused heavy CPU usage. For Win8, it only recompiles updated routines, and now much is done in the "cloud".

MsCorSvW stands for Microsoft Compiler To Save Work

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 mscorsvw.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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Mscorsvw.exe file information

Windows Task Manager with mscorsvw
Mscorsvw.exe process in Windows Task Manager

The process known as .NET Runtime Optimization Service (version v2.0.50727_X86) or Microsoft .NET Framework (version 4 Client Profile) or Windows Logon User Interface Host belongs to software Microsoft .NET Framework (version 4 Client Profile, 4 Client, 4, 4.5.2 Hotfix, 2.0 Service Pack) or Microsoft .NET Framework NGEN or Microsoft Windows Operating System by Microsoft (

Description: Mscorsvw.exe is not essential for the Windows OS and causes relatively few problems. The mscorsvw.exe file is located in a subfolder of C:\Windows or sometimes in a subfolder of "C:\Program Files" (mostly C:\Windows\Microsoft.NET\Framework\v4.0.30319\). Known file sizes on Windows 10/8/7/XP are 130,384 bytes (27% of all occurrences), 69,632 bytes and 41 more variants. 
It runs as service clr_optimization_v4.0.30319_32: Microsoft .NET Framework NGEN.
The program is not visible. Mscorsvw.exe is digitally signed. The file is not a Windows core file. You can uninstall this program in the Control Panel. Therefore the technical security rating is 19% dangerous; but you should also compare this rating with the user reviews.

Uninstalling this variant: There is a possibility to consult Microsoft’s Customer Service, see if there is a newer version or safely remove the program using the uninstall program of Microsoft .NET Framework (Control Panel ⇒ Uninstall a Program).

Recommended: Identify mscorsvw.exe related errors

Important: Some malware camouflages itself as mscorsvw.exe, particularly when located in the C:\Windows or C:\Windows\System32 folder, for example Win32:Malware-gen or AutoIt:Agent-OJ [Trj] (detected by Avast), and Trojan.Generic.KDV.824738 or Gen:Trojan.Heur.AutoIT.10 (detected by BitDefender). Therefore, you should check the mscorsvw.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

Avast detecting as Virus.
Ate up CPU for about 5 mins after 17 updates. Them vanished. No computer expert, but this sounds fairly typical. Don't sweat it, let it do its thing and in less than an hr it'll be over...
  Jake Bullet  
.net framework SHOULD ONLY BE DOWNLOAD FROM OFFICIAL MICROSOFT WEBSITE other companies such as softonic will ad perameters to allow popup ads to infest
  Trevor Goble  
it doesn't use much CPU, but it is continuously writing to the paging file even though I have half a gig of unused RAM!
This is a trojan horse confirmed by superantispyware. generally mscorsvw.exe is a .net file but trojan uses its name to fake it. it will suck up all your cpu resources and ultimately crash the computer or results in BSOD. it will hide itself in task manager and process explorer. check with tune up utilities, the process is showing running and using high cpu reources. search and delete the file.
  variz gupta  
To get rid of mscorsvw without breaking anything: Hit start, type "cmd", press Ctrl+Shift+Enter to start a command line in Administrator mode. Then "cd \windows\Microsoft.NET\Framework\vx.x.xxxx" (use the highest number) and type "ngen executequeueditems". This will do all the work that mscorsvw is supposed to do. It may take a while, but then its done and doesn't annoy you anymore. Note that this has to be repeated for every change to .net or any .net Program.
  nwp   (further information)
its harmless really , if only runs in the background for a short time to compile and speed up old ,NEt frameworks once its done its job it will stop taking all your CPU cores , its only dangerous if its not located within the windows/.NET framework folder
It wants to access the following IP's in this process, most owned by akamaitechnologies,,,,,, and many more - thanks to ZoneAlarm. Don't see the need for Akamai and the .NET framework, as it claims it for improving performance... Thanks MS or is it Akamai
More comments can be found here:
    (further information)

Rating chart

Summary: Average user rating of mscorsvw.exe: based on 73 votes with 9 reviews. 31 users think mscorsvw.exe is essential for Windows or an installed application. 14 users think it's probably harmless. 13 users think it's neither essential nor dangerous. 9 users suspect danger. 6 users think mscorsvw.exe is dangerous and recommend removing it. 9 users don't grade mscorsvw.exe ("not sure about it").

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Best practices for resolving mscorsvw issues

A clean and tidy computer is the key requirement for avoiding problems with mscorsvw. 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 mscorsvw.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

mscorsvw.exe [all]