What is is a Windows DLL file. DLL is the abbreviation for Dynamic Link Library. DLL files are needed by programs or web browser extensions, because they contain program code, data, and resources. The following information can help you determine if is a Windows system file or if it belongs to an application that you can trust.

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The process known as Microsoft Common Language Runtime Class Library belongs to software Microsoft .NET Framework by Microsoft (

Description: is not essential for Windows and will often cause problems. is located in a subfolder of C:\Windows. Known file sizes on Windows 10/8/7/XP are 11,486,720 bytes (26% of all occurrences), 11,497,984 bytes and 8 more variants. 
A .dll file (Dynamic Link Library) is a special type of Windows program containing functions that other programs can call. This .dll file can be injected to all running processes and can change or manipulate their behavior. The program is not visible. There is no detailed description of this service. It can change the behavior of other programs or manipulate other programs. The file is not a Windows system file. Therefore the technical security rating is 66% dangerous, however you should also read the user reviews.

Recommended: Identify related errors

Important: Some malware camouflages itself as Therefore, you should check the 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

Suspicious file located in NativeImages trying to access the registry, seems to be a false positive for people running Windows 7, but I am running Vista and my computer has been lightning fast ever since I blocked it.
  nanashi   (further information)
I did a Rating Scan with my newly installed Comodo Pro 7 security system (of which I am enormously proud) and it unearthed this 'mscorlib' character plus another 11 closely related mystery files . They got in somehow or other about a month ago. I have no recollection of the event but that needn't necessarily mean I wasn't there or, indeed, that it wasn't me who opened the door. ( Btw, however they got in, it would've happened before I got Comodo so there's no suggestion of any failure there.) Anyway, what's annoying me now is that I can't access the "nativeimages" location where the files now lurk because the location itself is not where it should be (in "system assembly") and no amount of searching to date has found it anywhere else. So I can't even get a look at any of these unknown files/apps/wtfs to try and work out if they are good or evil. Increasingly woman's instinct (my No 1 resource in all such investigations) is telling me to not trust a single one of them ~ that the whole secretive little ni.dll clique is rotten to the core and should be sent back to the hell from whence they came! But am I being irrational? Well, anyway, that's where I'm at. I shall continue sleuthing away here and will report back when there's more to report. Over and out

Summary: Average user rating of based on 2 votes with 2 user comments. 2 users suspect danger.

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Best practices for resolving mscorlib issues

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

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