Building Unreal Engine from source may be a dauting task, but it's not as hard as it seems. Honestly, it requires more patience and attention than anything else. This guide aims to help you through the entire process, from downloading the source code to building the Engine itself.

• Building from source
  • Before we begin
    • A note on Angelscript
  • Step-by-step
    • Accessing the source code
    • Downloading the source code
    • Installing the prerequisites
    • Enabling Windows Debugging Tools
    • Commencing the build!
    • Running the Editor
  • Troubleshooting
• Creating an Installed Build
  • What is an Installed Build?
  • Is an Installed Build for me?
  • Before we begin
  • Step-by-step
    • Building the Automation Tool
    • Creating the Install Build script
    • Installing the prerequisites
      • Downloading Visual Studio 2019
      • Getting .NET 4.5
    • Running the script
    • Distributing your fresh Installed Build
  • Troubleshooting
• General references
• FAQ

Make sure you have the following:

• Approximately 240GB of free space, ideally in an SSD. This includes Visual Studio and the dependencies.
• At the very least 2h of your time. Can be way more depending on your hardware and any issues you find along the way.
• Lots of patience and attention.

Also, at the time of writing, the procedure below was only tested on Windows 11 with Visual Studio 2022 targeting Win64 Development/Shipping builds, in the following machine:

i9 11900K Processor

64 GB RAM DDR4

1TB SSD Samsung QVO 870

Note that most mid-end+ machines will do the trick—don't worry too much about it. However, the more CPU and RAM you have, the quicker the process will be.

If you're still unsure your machine can handle it, please refer to this post.

If you are aiming to build Unreal-Angelscript, the procedure documented next is almost the same, with the exception of the source code you need to download. But don't worry about it for now—follow the steps below and the differences will be properly flagged as you go.

If you are unsure as to why you would want to build from source for Angelscript, please refer to the FAQ section.

If you are reading this having nothing to do with Angelscript, then you can safely ignore this section and all the references to Angelscript for the rest of the document—they are not relevant to you.

Please, make sure you follow all the steps listed below in order, with your greatest attention.

Regardless whether you're aiming Angelscript or a vanilla Unreal Engine version, you need to have access to the Epic Game's organization on GitHub. In order to get that, please refer to Epic's official guide.

Now that you have access to Unreal Engine's source code, it's time to download it.

1. Create a new folder on your machine, preferably in a not-so-nested path. An ideal place would be something like C:\UE-Git. The name does not really matter, just try to keep the path short to avoid issues later.

2. Head to the Unreal Engine's Repository.

👼 Angelscript people: instead of the link above, please use this one.

3. Click on the green button that says "Code" and then click on "Download ZIP".

4. Extract the ZIP file to the folder you created in step 1.

First, if you still don't have Visual Studio 2022, download it from here. For what it's worth, the Community Edition was used in this procedure.

During install, through the Visual Studio Installer, you may land at a screen similar to this:

If you already have Visual Studio 2022 installed, then just open Visual Studio Installer and click "Modify" on your Visual Studio 2022 entry to get to the window above.

Now, these are the Workloads you want to install (or make sure it's installed):

• Desktop development with C++
• Game development with C++
• .NET desktop development

If you didn't notice, the "Workloads" I am referring to is the very first tab on the window above.

You probably don't need each and every of the individual components the Workflows above install, but I didn't have success by nitpicking them despite all my efforts. I was only successful by installing the Workloads above in their entirety. Please, if you have more intel on this, file an issue.

But wait, there's more! To increase our chances of success, we're going to install a few more things. Open the Individual Components tab, located right next to the Workloads tab, and make sure the following are, or will be, installed:

• Windows 10 SDK (10.0.18362.0)
• .NET 6.0 Runtime (Long Term Support)
• .NET Framework 4.6.2 targeting pack

This is important because a common mistake during the build process is that you don't have the right SDKs/versions installed. The versions I'm referring to are the ones mentioned by Epic itself on their Unreal Engine 5.1 Release Notes:

I'd like to acknowledge I'm not really sure everybody needs this step because some other tutorials didn't mention it. However, I had to do it myself in order to get the build to work, so I'm including it here just in case.

1. Open your Windows Search bar and search for "Settings" and open it:

2. Open the "Apps" tab:

3. Click on "Installed apps":

4. Search for 10.0.18. You should see Windows Software Development Kit - Windows 10.0.18362.1, like so:

If you are not seeing this app, make sure you installed the Windows 10 SDK (10.0.18362.0) as described by the Installing the prerequisites step.

1. Click on the elipsis (...) and then click on "Modify". This window may show up:

6. Mark the "Change" option and then click on "Next". In the window that just showed up, mark the Debugging Tools for Windows checkbox and click on "Change":

This step is required for both Angelscript and/or vanilla Unreal Engine.

At this point, you should have everything you need to build from source. Let's get to it!

1. Open the folder you unzipped the source code to. You should see a file called Setup.bat. Double click on it to run it. This may take a while, so be patient. It usually takes 10-20 minutes to me.
2. Once the Setup.bat finishes, you should see a new file called GenerateProjectFiles.bat. Double click on it to run it. This should be quick.
3. Now open the UE5.sln file that was just created. This is the Visual Studio solution file for Unreal Engine. It's in the same folder as the GenerateProjectFiles.bat file.
4. Now that you're on Visual Studio, you need to select the Development Editor configuration. You can do that by clicking on the dropdown below the Build and Debug menus at the very top of the window:

5. You also need to select the Win64 platform. You can do that by clicking on the dropdown right next to the Development Editor configuration:

6. You're ready to build! At your right sidebar, you should see a Solution Explorer panel. Uncollapse the Engine folder and you should see the UE5 project:

7. Right-click on it and select Build.

8. Now it's tea time! This process will take a while, so be patient and go grab a cup of tea. It may take anywhere from 1:30 to 3 hours or even more, depending on your machine.

1. Phew! You made it! Let's first certify everything worked as expected. At this point, your Visual Studio should be displaying something like this in the Output panel:

2. Before you run the editor, right click on the UE5 project and select Set as Startup Project:

3. To finally run your juicy new editor, right click again on the UE5 project and select Debug > Start new instance. This should open the Unreal Engine 5.1 Splash Screen.

Note that the very first time you run the editor, it will take a little while to load. This is normal. It is indexing stuff, compiling shaders, etc, so be patient—the next time you run it, it should be faster.

If you're having any kind of trouble with the build process:

1. Make sure you have enough space.
2. Make sure your computer meets the minimum requirements.
3. Make sure you have the right versions of the prerequisites installed.
4. Make sure you granted the right permissions to the folder you are compiling to.
5. Make sure you are building a pristine copy of the source code. Don't try making changes to the Engine prior to the building process.
6. Avoid long paths. Try to keep the path to the source code folder as short as possible. For example, if you are compiling to C:\Users\YourName\Documents\UnrealEngine, try compiling to C:\UnrealEngine instead.
7. If you are cloning the source code via Git, make sure you are doing it from the release branch. Also, it's advised to clone using --depth 1 to avoid downloading the entire history of the repository and save some time and space.

If none of the above works, please open an issue on this repository and I'll try to help you out. If you're seeking a swifter solution, you can also try asking for help on the Unreal Slackers Discord Server via the #engine-source channel.

Ultra important: try to be as specific as possible when describing your problem. Save the time of people willing to help you, and they'll save you the time of having to wait for a response. Also, be patient.

Alright. You've built the engine from source. It was a long and arduous journey, but you made it. Now, you want to start creating your game on the top of it but you realised that Billy, your teammate, also needs the same engine you now have.

Then you also realised that the weight of this engine of yours is 180GB+ and you have no clue how to send it to Billy.

Now what?

Well, you have plenty of options.

• You can literally zip your 180GB+ and send it over.
• You can ask Billy to build the engine from source himself, but hey, Billy doesn't even remember what Visual Studio is.
• Or you can create an Installed Build!

Note to AngelScript people: this guide also applies to you as is!

The quickest example of what an Installed Build is, is the retail version of Unreal Engine—the one you download from the Epic Games' Launcher. That is an Installed Build.

Installed Builds are compiled versions of the Engine that can be distributed to other people out-of-the-box, with almost no hassle. They are smaller than the source code version and mostly only requires you to zip it and send it about.

I introduced this section with the Billy example, where an Installed Build would be useful if you wanted to share your engine with someone else—but other scenarios are:

• If you just wanted to make one small tweak to the source code of the engine and nothing more. In this case, you can generate an Installed Build and get rid of the source code, saving you some disk space.
• It already happened to me to change a C++ file in the scope of my project and, for some reason, the entire engine started compiling again—and I don't remember playing with the Intermediate folder. If you are afraid of that and your work with the Engine code is done, you can generate an Installed Build and get rid of the source code—which also saves you some disk space.
• If you only built from source because of Dedicated Servers, you can generate an Installed Build of the Engine with the Dedicated Server support and get rid of the source code.
• My most recent case may be a little bit more specific, but it's a case nonetheless: I just wanted a "lighter" version of the 5.1 Engine with Angelscript.

Ok, so you want to create an Installed Build. That's great! But before you do that, you need to know a few things:

• You need to comply with all the things described by the Building from Source section, as well as having the built from source engine successfully built.
• You're going to need ≈100GB of (extra) free space, ideally in an SSD. Yes, all that space to build the engine from source plus ≈100GB.
• You're going to need lots of patience. In my experience, this process takes at least twice as much time as building the engine from source. It's a very slow process, so keep calm. Note that the time may vary depending on your hardware.]
• If you have the luxury of having yet another extra ≈180GB lyring around, I'd recommend you backing up your source code folder before venturing into Installed Builds. The first time I generated the Installed Build, it failed silently and messed up my source code folder. In short, I had to start the process of building from source all over again. I was definitely not happy, specially after waiting for more or less 4 hours to finish the Install Build process only to have it double fail: one for the Install Build itself and another for the engine build.

Most of the credits here go to Joe, from Asset Pack Games, who published an excellent video on how to create an Installed Build. I've just tested it myself with the latest version of the Engine (5.1 at the time of writing), tweaked a few things and, of course, ported to a text-based guide.

1. Open UE5.sln in Visual Studio.
2. At the right sidebar, you should see a Solution Explorer panel. Uncollapse the Programs folder and locate the AutomationTool project:

3. Right-click on it and select Build. It should be quick.

1. Open the folder where your engine is located. If you followed the steps in the Building from Source section, it should be located at C:\UE-Git.
2. Create a new file called GenerateInstalledBuild.bat and paste the following code into it:

echo off

:: Move to the AutomationTool folder.
cd Engine\Binaries\DotNET\AutomationTool

:: The actual script, which will generate the Installed Build using the Automation Tool and the BuildGraph.
AutomationTool.exe BuildGraph -target="Make Installed Build Win64" -script=Engine/Build/InstalledEngineBuild.xml -set:HostPlatformOnly=true

:: Just an empty line to separate the outputs.
echo.

:: Just a friendly reminder to the user that the process is done.
echo. Install Build Generate Script complete

:: The `pause` below prevents the window from closing immediately after the script finishes running.
pause

Important: make sure this file is sitting at the same level as the Engine folder, at the same level of the UE5.sln or the GenerateProjectFiles.bat files.

This script is really important. It's the script that will actually generate the Installed Build. Let's zoom in in the most important part of it:

cd Engine\Binaries\DotNET\AutomationTool AutomationTool.exe BuildGraph -target="Make Installed Build Win64" -script=Engine/Build/InstalledEngineBuild.xml -set:HostPlatformOnly=true

Now, breaking it down:

• cd Engine\Binaries\DotNET\AutomationTool changes the current directory to the Automation Tool's folder.
• AutomationTool.exe is the actual Automation Tool executable.
• BuildGraph is the command to generate the Installed Build itself.
• -target="Make Installed Build Win64" specifies the target the BuildGraph will run against. In this case, Win64 (it could be Mac, for example).
• -script=Engine/Build/InstalledEngineBuild.xml is the path to the file that describes all the default parameters BuildGraph will be using to generate the Installed Build.
• -set:HostPlatformOnly=true is a flag that will tell the BuildGraph to build only for the current platform. If you're in a 64-bit Windows machine, it will only build for 64-bit Windows.

All these options are officially covered by the Using an Installed Build documentation. It's quite outdated, but still a good reference. I recommend you to read it.

If you want to learn more about the most up-to-date parameters, it would be best if you check the Engine/Build/InstalledEngineBuild.xml file where most parameters are described.

To translate this into a more human-readable version, the script above is saying:

Hey, Automation Tool! I want you to generate an Installed Build for the Win64 platform, using the defaults specified by Engine/Build/InstalledEngineBuild.xml with the exception that I want to target only my current platform (which is also Win64, hehe.).

All of the above to say: customise this script as much as you like to fit your needs.

3. Save the file and close it.

I intentionally chose not to include this step earlier because I didn't want to cause confusion.

Before you run the script, there's one extra step though, which is installing Visual Studio 2019. The reason why, you may ask, it's because it includes .NET 4.5 which is required for UBT. If you don't do this, you are prone to spend hours generating your Install Build to have it fail at the end.

1. Head to this page.
2. Log in with your Microsoft account.
3. Download the Community version of Visual Studio 2019:

1. Run the installer you just downloaded.
2. Once do, you should be seeing a window like this:

3. Click on Modify in your Visual Studio 2019 installation.
4. Select .NET desktop development and click Modify:

If you want a cleaaner installation of Visual Studio 2019, you can uncheck some optional components once you selected the .NET desktop development option:

Finally fasten your belt because it's show time.

1. Run the GenerateInstalledBuild.bat script you just created.
2. Wait.
3. Wait.
4. Wait.
5. & wait.

This process is really long. Just to give you a glimpse, I tried it a few times with different parameters and it took me:

• 1st run: ≈4:30h
• 2nd run: ≈2:59h (had a few things cached from the prev run)
• 3rd run: ≈6:53h (clean cache, different parameters from the last two runs)

If everything went well, you should see a LocalBuilds folder at the same level as the Engine folder as well as no errors in the console.

Now that you have your Installed Build, you can distribute it out and about. And there's nothing special here, really. You just zip the LocalBuilds/Engine folder and you should be good to go.

1. Make sure you went through the Building from Source section.
2. Make sure you went through the Troubleshooting from the Building from Source section.
3. It's very possible that it will cost you a lot of time until an error from the InstallBuild script pops up. One way to mitigate that is by forcing an expected error to happen. For example, if you're building for Win64, you can force the script to fail by changing the -target parameter to -target="Make Installed Build Mac". This way, you're going to know if the script is working or not much quicker than waiting for the whole process to finish.

• Unreal Slackers Discord Server
• Unreal Engine Recommended Specifications
• Using an Installed Build
• UE5 Tutorial - Creating a Custom Install Build

git clone [email protected]:EpicGames/UnrealEngine.git --depth=1