Unreal Engine 4.12 Download ((link)) -
The easiest way to install UE 4.12 is directly through Epic's official desktop client.
Unreal Engine 4.12, released on June 1, 2016, is a significant legacy version of the engine that introduced major features like the cinematic editor and a preview of the Unreal Engine How to Download Unreal Engine 4.12 The standard method to download this version is through the Epic Games Launcher Unreal Engine 4.12 Download
Extract the files, run Setup.bat to download the required dependencies, and then run GenerateProjectFiles.bat to create the Visual Studio solution file. System Requirements for Unreal Engine 4.12 The easiest way to install UE 4
To help you get your project running smoothly on this specific build, tell me: What and hardware specs are you using? Are you planning to build a game for PC, mobile, or VR ? Are you planning to build a game for PC, mobile, or VR
If you want, I can produce exact command lines for cloning and building 4.12 on Windows (Visual Studio) or macOS — tell me your OS and whether you prefer prebuilt or source.