physxloader.dll
This file belongs to NVIDIA PhysX System Software. Install that package and the DLL arrives with it, in the right place and correctly registered.
Do not download this DLL on its own
Searching for a missing DLL by name leads to sites that hand you that single file. It is one of the oldest and most effective malware delivery methods there is, and a system DLL from an unknown source is indistinguishable from a deliberately modified one. There is never a legitimate reason to obtain a runtime component that way.
What it is
The loader for NVIDIA PhysX, the physics engine a number of games use. It comes with the PhysX System Software rather than with the graphics driver.
Where you see it: Games using PhysX for cloth, debris and fluid effects.
You do not need an NVIDIA graphics card. PhysX falls back to the processor, so the runtime is worth installing on AMD and Intel systems too.
Install NVIDIA PhysX System Software
The official package, with the download URL Microsoft declares and the SHA-256 of every installer so you can verify it before running.
After downloading you can check the file against our index to confirm it is the installer the publisher shipped.