ntdll.dll is a Dynamic Link Library (DLL) file used by Windows XP, Windows Vista and Windows 7.
It is also present in other versions of Windows such as Windows 8, 8.1 and 10, although the actual file name may differ from ntdll.dll.
What is a dll file?
A dynamic link library, or DLL, is a type of executable file that contains code and resources. These files are used by several kinds of programs including Windows system processes.
When you select the option to open a program in Windows, the program opens up and can be used by you in various ways.
However, as soon as you close that program, it is removed from your computer and your computer returns to its default state. In order to create a program that remains present on your computer all the time, dynamic link library files are used.
What Are Dynamic Link Libraries Used For?
As the name suggests, dynamic link libraries are part of a process that allows various programs to interact with each other.
As a developer, you can use a dynamic link library to bring the features of another program onto your own, which means that you don’t have to duplicate these features in your own code.
The ntdll.dll file is located in the C:\Windows\System32 directory of Windows operating systems and performs several important functions for these versions of Windows.
How big is ntdll?
The size of the ntdll.dll file varies depending on which version of Windows it is installed in, however the average size of the file is approximately 607KB.
If you are using a 64-bit version of Windows the file size will be larger as it will be occupying both operating system directories, i.e., C:\Windows\System32 and C:\Windows\SysWOW64.
Is It Safe?
As ntdll.dll is a Windows operating system file, it is unlikely to cause damage or other issues in your computer. However, the sheer size of this file has led many security experts to question why such a large file is necessary on most computers.
The truth is that ntdll.dll can be replaced with another version of the DLL without affecting your computer at all, and some security experts suggest that malware creators only use this name to fool users into thinking the file causes harm.
How Can You Tell if ntdll.dll Is Legit or a Virus?
Although ntdll.dll comes from the Windows operating system, it can be replaced without causing any damage to your computer.
In fact, it is a very common practice for malware creators to use the name of a legitimate file because they know that many users are too worried about losing their files to waste time doing research on them.
Are there any Legitimate Reasons for Having ntdll.dll?
The ntdll.dll process is required by the operating system, so if you are using a legitimate version of Windows then you will have this file in your computer.
However, if malware creators use the name of a legitimate file it is possible to cause damage to your computer without realizing it.
So should I remove ntdll.dll?
If you want to significantly reduce the size of the Windows operating system, then you can safely delete this file and replace it with an updated version.
However, for most users a safe file is probably not necessary, although it is likely that your computer will run faster and more efficiently if you have the latest version of ntdll.dll installed on your system.
How do i find ntdll.dll?
You should find the ntdll.dll file inside the Windows directory, which is typically located in C:\Windows.
You can also find various helper files within this directory such as ntdsapi.dll and pacer.sys, and you may also find other files with these names if your system has been infected with malware that tries to piggyback on your legitimate software programs.
How do i remove ntdll.dll?
To replace or remove the file, you must have administrative privileges on your computer.
You can easily replace this file by copying a newer version of the DLL to the appropriate Windows directory, but if you want to remove it from your system entirely you should use a special cleaning utility for this purpose.