Here is the information regarding downloading the Unreal Engine 4 offline installer.
This requires Visual Studio, MS Build, and ~40 GB of free space. Not beginner-friendly, but perfect for engine modifications.
If you have an existing installation, you can manually move the files and use the Epic Games Launcher to "verify" the files, which skips the large download. Unreal Engine 4 Download Offline Installer
A practical workaround for individuals with limited internet on their primary workstation is to use a secondary computer to download the engine through the launcher and then transfer it. Offline Installer of Unreal Engine - Epic Games Developers
Epic’s EULA requires the launcher for distribution, but for personal offline archiving, this tool is a lifesaver. Here is the information regarding downloading the Unreal
: A full installation can take up a massive amount of space; building from source can exceed depending on the components selected. Performance
Many users mistakenly search for "UE4 offline installer exe" and find malicious fake files. Instead, Epic provides the complete source code and build tools via GitHub. You must generate the installer yourself. If you have an existing installation, you can
: Developers who want a permanent, local copy of a specific engine version that won't be affected by launcher updates or server outages. Offline Installer of Unreal Engine - Epic Games Developers
Despite the lack of an official installer, developers needing an "offline" solution have legitimate workarounds, particularly for setting up development labs, home computers without internet, or preserving a specific engine version. The most reliable method is to use the Epic Games Launcher on a machine with internet access to perform a full, clean installation of the desired UE4 version. Once installed, the entire engine directory (typically located in C:\Program Files\Epic Games\UE_4.27 for version 4.27) can be compressed (e.g., using 7-Zip or WinRAR) and copied to external media like a portable hard drive or a set of USB flash drives. This compressed archive effectively becomes a custom offline installer. To deploy it on an offline machine, one simply extracts the archive to the same path and manually creates any necessary shortcuts. However, this method has caveats: it will not register the engine with the Launcher on the target machine, and certain components tied to Visual Studio or platform SDKs may require separate offline installation.