Download Unreal Engine 4.27 Offline Installer Fix

Unfortunately, Epic Games does not provide an official, single-file offline installer for Unreal Engine 4.27 (or any recent version). The standard installation method requires the Epic Games Launcher to download and verify files.

Step 3: Generate the Offline Installer

On your online machine, go to the Unreal Engine GitHub repository.
Ensure your GitHub account is linked to your Epic Games account.
Go to the "Tags" tab and download the ZIP file for the 4.27 release.
Transfer this ZIP file (via USB) to your offline machine.
Extract the ZIP and run the Setup.bat file. (Note: Even for an offline install, Setup.bat usually requires an initial internet connection to fetch third-party dependencies like DirectX, PhysX, etc. If you are 100% offline, you must also download the cached dependencies ZIP from GitHub and place it in the same folder before running Setup.bat).
After Setup.bat finishes, right-click the GenerateProjectFiles.bat file and run it.
Open the resulting UE4.sln file in Visual Studio, set the build configuration to "Development Editor", and build the project.

Link your account: Log into Epic Games, go to Account → Connected Accounts → GitHub, and link them.
Accept invite: After linking, you’ll receive access to https://github.com/EpicGames/UnrealEngine.
Clone the specific 4.27 tag: Open terminal or command prompt and run:
```
git clone --branch 4.27.2-release --single-branch https://github.com/EpicGames/UnrealEngine.git
```
This downloads the complete source code and binaries (approx. 20-28 GB).
Build from source (optional): If you need the pre-compiled editor (the "binary" build), you must run Setup.bat and GenerateProjectFiles.bat, then build in Visual Studio.

Archive.org

There are trusted sources like where users have uploaded complete UE 4.27.2 offline packages. Example search string: download unreal engine 4.27 offline installer