What is rundll33.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 rundll33.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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Rundll33.exe file information

The process known as Run a DLL as an App or Eine DLL-Datei als Anwendung ausführen belongs to software Microsoft Windows Operating System or Betriebssystem Microsoft Windows by Microsoft (

Description: Rundll33.exe is not essential for Windows and will often cause problems. Rundll33.exe is located in a subfolder of C:\Windows\System32. Known file sizes on Windows 10/8/7/XP are 50,688 bytes (75% of all occurrences) or 33,280 bytes. 
It is not a Windows core file. The program is not visible. Rundll33.exe is an unknown file in the Windows folder. Therefore the technical security rating is 33% dangerous, however you should also read the user reviews.

Recommended: Identify rundll33.exe related errors

If rundll33.exe is located in a subfolder of C:\, the security rating is 64% dangerous. The file size is 6,241,792 bytes. The program has no file description. The program is not visible. The program starts upon Windows startup (see Registry key: Run). The rundll33.exe file is not a Windows system file.

Important: Some malware also uses the file name rundll33.exe, for example PE_VIRUX.A-6 (detected by TrendMicro), and Virus.Win32.Virut.ce (detected by Kaspersky). Therefore, you should check the rundll33.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's a part of TSPY.POPHOT.VP

Summary: Average user rating of rundll33.exe: based on 2 votes with 1 user comment. One user suspects danger. One user thinks rundll33.exe is dangerous and recommends removing it.

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Best practices for resolving rundll33 issues

A clean and tidy computer is the key requirement for avoiding problems with rundll33. 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 rundll33.exe 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

rundll33.exe [all]