DirectX 9 / 10 / 11 Runtime Overview
The DirectX End-User Runtime is a free Microsoft package for Windows that installs legacy DirectX components — particularly the D3DX, XInput, XAudio, and other helper libraries from DirectX 9, 10, and 11 eras — that some games and applications still require. Modern Windows already includes the core DirectX, but many older (and even some newer) games were built against these additional redistributable libraries and will show a missing-DLL error (such as d3dx9_43.dll) without them. Installing the runtime adds those components so the affected software runs. It does not replace the version of DirectX built into Windows. The offline installer installs these components without an internet connection. Running the installer is harmless on systems that already have the components, since it simply verifies and adds only the ones that are missing. The link on this page goes to Microsoft's official DirectX 9 / 10 / 11 Runtime download.