Downloading Unreal Engine Source Code

Accessing Unreal Engine Source Code on GitHub

Unreal Engine includes full access to the complete C++ source code, so you can study, customize, extend, and debug the entire Unreal Engine, and complete your project without obstruction.

Our source code repository on GitHub is continually updated as we develop features in our own mainline, so you don’t even have to wait for the next product release to get your hands on the very latest code.

To access Unreal Engine source code, do the following:

1. Navigate to GitHub and sign up for an account.

2. Sign in to UnrealEngine.com with your verified Epic Games account. To open your account dashboard, hover over your username, and select Personal from the drop-down menu.

3. With your account dashboard open, select the Connections tab from the sidebar. Select the Accounts tab, and then select the Connect button below the GitHub icon.

4. If you have not already signed the Unreal Engine End User License Agreement, you will need to read through its terms and select the check box, then select Link Account. If you are signed out of your GitHub account, you will be directed to GitHub to sign in after clicking the Link Account button.

5. To complete the OAuth App Authorization process, click the Authorize EpicGames button. You can learn more about this process in GitHub’s overview on Authorizing OAuth Apps.

6. GitHub will send an email inviting you to join the @EpicGames organization on GitHub. You must select the Join @EpicGames button in this email within seven days to complete the GitHub and Epic Games account linking process.

Upon completion, you will receive an email from Epic Games verifying that your GitHub and Epic Games accounts were successfully linked. If you don’t receive a confirmation email, or if your account is experiencing problems, get help from Customer Service. You are now ready to get started by going to our GitHub page (login required) to download the full source code.

Source Code Branches

You'll notice that we've published UE's source code in several branches.

Branches whose names contain dev, staging, and test are typically for internal Epic processes, and are rarely useful for end-users Other short-lived branches may appear from time to time as we stabilize new releases or hotfixes.

Release Branch

The Release branch always reflects the current official release. These are extensively tested by our QA team, so they make a great starting point for learning Unreal Engine and for making your own projects. We work hard to make releases stable and reliable, and aim to publish a new release every few months.

Main Branch

Most active development on UE happens in the ue5-main branch. This branch reflects the latest release of the engine and may be buggy or it may not compile. We make it available for developers who are eager to test new features or work in lock-step development with us.

Setting up a Perforce Server on your Local Machine

There are two ways of running the Perforce server, P4D and P4S. P4D runs while an instance of the command line is running, so it is usually only used for spot-maintenance tasks. P4S is the service-based equivalent of P4D as it allows you to run the server in the background. The service is usually installed and started when you install the Perforce server tools.

Once the service is running, you can connect to your server using P4Admin. If this is the first connection to your server, then you can make a new user in the initial connection dialog:

Fill in the connection information for your Perforce server and press okay. Once you have connected to the server in P4Admin, you can make new depots, users, and groups pretty easily. Use P4V and the Unreal Editor to connect to the server with the credentials you supplied in the initial connection dialog.

P4 Typemap

Before you start adding files to your depot, you should set up your P4 Typemap so Perforce knows how to treat Unreal file types. Setting the typemap will affect how files get set to read only or writable inside of Perforce. However to do this, you will need to open a new command prompt and set up some p4 environment variables.

	p4 set P4USER=your.username
	p4 set P4PORT=localhost:1666
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Replace the values above with your respective username and connection address. Open the typemap by entering the following in the command prompt.

	p4 -P <PASSWORD> typemap
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You will then see a text window open; this is your server's typemap. The typemap below is an example that we have used in the past:

	# Perforce File Type Mapping Specifications.
	#
	#  TypeMap:             a list of filetype mappings; one per line.
	#                       Each line has two elements:
	#
	#                       Filetype: The filetype to use on 'p4 add'.
	#
	#                       Path:     File pattern which will use this filetype.
	#
	# See 'p4 help typemap' for more information.

	TypeMap:
					binary+w //depot/....exe
					binary+w //depot/....dll
					binary+w //depot/....lib
					binary+w //depot/....app
					binary+w //depot/....dylib
					binary+w //depot/....stub
					binary+w //depot/....ipa
					binary //depot/....bmp
					text //depot/....ini
					text //depot/....config
					text //depot/....cpp
					text //depot/....h
					text //depot/....c
					text //depot/....cs
					text //depot/....m
					text //depot/....mm
					text //depot/....py
					binary+l //depot/....uasset
					binary+l //depot/....umap
					binary+l //depot/....upk
					binary+l //depot/....udk
					binary+l //depot/....ubulk
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Once edited, save the file by pressing Ctrl+S on your keyboard and then exit. The command prompt should then show Typemap saved.

P4 Ignore

There might be files that you want ignored when addign client files to the depot or when reconciling client workspaces. To help with this, you can specify a P4 Ignore file. The default name for this file is .p4ignore.

The following is an example of Epic's .p4ignore file:

	# Here you can specify files to ignore when adding files to the depot.
	#
	# The syntax for P4IGNORE files is not the same as Perforce syntax.
	# Instead, it is similar to that used by other versioning systems:
	#
	# - Files are specified in local syntax
	# - a # character at the beginning of a line denotes a comment
	# - a ! character at the beginning of a line excludes the file specification
	# - a * wildcard matches substrings.
	#
	# For example:
	#
	# foo.txt    Ignore files called "foo.txt"
	# *.exe      Ignore all executables
	# !bar.exe   Exclude bar.exe from being ignored
	#
	###############################################################################
	# Epic's P4IGNORE.
	# P4IGNORE doesn't work like GITIGNORE:
	# http://stackoverflow.com/questions/18240084/how-does-perforce-ignore-file-syntax-differ-from-gitignore-syntax
	###############################################################################
	# Ignore root Visual Studio solution files. We do check in some sln files in subdirectories, so only ignore
	# the ones found in the root.
	/*.sln
	/.p4sync.txt

	# Ignore all Visual Studio temp files.
	*.suo
	*.opensdf
	*.sdf
	/Engine/DerivedDataCache/*
	**/DerivedDataCache/Boot.ddc
	**/DerivedDataCache/**/*.udd

	# Ignore all Intermediate and Saved directories
	*/Intermediate/*
	*/Saved/*
	# Ignore UBT's configuration.xml
	Engine/Programs/UnrealBuildTool/*
	*.uatbuildrecord
	*.tmp

	# Ignore built binaries and temporary build files
	*/obj/*
	*.csprojAssemblyReference.cache

	# Ignore UBT's log output files
	/Engine/Programs/UnrealBuildTool/*.txt

	# Ignore Python cached files
	*.pyc

	# Ignore JetBrain's IDE folders
	.idea/
	!.idea/runConfigurations
	.gradle/

	# Ignore autogenerated files from HoloLens WMRInterop
	/Engine/Source/ThirdParty/WindowsMixedRealityInterop/packages/*
	/Engine/Source/ThirdParty/WindowsMixedRealityInterop/MixedRealityInteropHoloLens/Generated Files/*
	/Engine/Source/ThirdParty/WindowsMixedRealityInterop/MixedRealityInteropHoloLens/x64/*
	/Engine/Source/ThirdParty/WindowsMixedRealityInterop/MixedRealityInteropHoloLens/ARM64/*
	/Engine/Source/ThirdParty/WindowsMixedRealityInterop/MixedRealityInterop/x64/*
	/Engine/Source/ThirdParty/WindowsMixedRealityInterop/MixedRealityInterop/ARM64/*

	# Ignore files added by Finder on Mac
	.DS_Store

	# Ignore all .code-workspace files
	*.code-workspace
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For more information about ignore files, see the P4IGNORE documentation page on Perforce's documentation site.

Server on your Local Network

You can set up a server on your local network for people to use to collaborate with one another. To do this, follow the steps above on the server and connect using the server's name or IP from your clients.

Cloud Provider

There are various cloud providers that allow you to host Perforce servers off-site and to collaborate remotely. A quick search online for Perforce Hosting should turn up a few results. Each hosting provider is different, but all should end up with a set of credentials that you can use to connect. See also Connecting from Unreal Editor below for a note about connecting to Perforce cloud providers.

Setting up a Local Workspace

To work with files that are under Perforce control, you will need to set up a Workspace so that the files can be managed on your local machine. You can do this via P4V by opening up the Workspaces tab in the View dropdown:

To create a new workspace, right-click in the Workspace window and select the New Workspace option. Then enter a name for your workspace and a location where you want the files to be on your local machine, the Workspace Root.

Once you have a server and a workspace, you will want to start adding files to it. For the moment, this needs to be done initially outside the Editor via P4V. If you already have a workspace that someone else has set up with some files already, you can skip ahead. When you create a new project, you can choose whether it incorporates C++ code and Blueprint elements. If you are using C++ code in your project, you will see a Source/ directory as well. You should initially add only the following directories of your project:

Folders and files highlighted in Green should be added to your depot. The Binaries folder in Yellow is optional, depending on how your team wants to work together. It is not required if every team member is going to compile their editor/game themselves, but should be included in the initial add if any team members will just be grabbing a version from the depot to create content. Note that the server typemap setup above should mean that coders can compile their binaries without them being set to be Read-Only by Perforce.

Adding Files to Perforce

Adding files to Perforce is something that can be accomplished in the few following steps.

1. To add files/folders to Perforce, first select the files/folders in P4V and then right-click and select the Mark For Add option.

   

2. This will add the files to your default change list. All files that you add can be seen in the Pending change lists tab:

   

3. To submit something, first right-click on the change list and then select Submit. Then enter a change list description and click the Submit button.

   

If you want to start work on a project that someone else has already started, you will need to get the latest revision from Perforce using P4V. To do this, find the project in the Depot View in P4V and then Right-click on the project you want to get and select Get Latest Revision. This will download all the files to the location you specified for your Workspace Root above.

Connecting from Unreal Editor

You can connect to your Perforce server right from the Editor by clicking on the Source Control icon on the Toolbar:

Once open, choose Perforce as the provider from the Source Control Login dialog and enter your login credentials. If you have a workspace already set up (that the current project is inside of), your login credentials should be populated automatically.

When using some servers, including many cloud providers - you may need to enter the Host and Password to access your depot from the Editor. You can do this by opening the advanced field at the bottom of the Perforce login dialog:

Downloading the Source Code

Please follow these instructions to download the Unreal Engine source code.

Additional target platforms

• Android support will be downloaded by the setup script if you have the Android NDK installed. See the Android Quick Start guide.

• iOS development requires a Mac. Instructions are in the iOS Quick Start guide.

• Development for consoles and other platforms with restricted access, like Sony PlayStation, Microsoft Xbox, and Nintendo Switch, is only possible if you have a registered developer account with those third-party vendors.

Depending on the platform, additional documentation or guidance may be available in the Unreal Developer Network support site, or as a downloadable archive in the section of the Unreal Engine Forums that is dedicated to your platform.

If you don't have access to these resources, first register a developer account with the third party vendor. Then contact your Epic Games account manager if you have one, or fill out and submit the Console Development Request form for Unreal Engine if you don't. Epic will contact you with a formal agreement to digitally sign. Once this is approved, you will receive instructions on how to access source code, binaries, and additional instructions for your platform.

Licensing and Contribution

Your access to and use of Unreal Engine on GitHub is governed by the Unreal Engine End User License Agreement. If you don't agree to those terms, as amended from time to time, you are not permitted to access or use Unreal Engine.

We welcome any contributions to Unreal Engine development through pull requests on GitHub. Most of our active development is in the master branch, so we prefer to take pull requests there (particularly for new features). We try to make sure that all new code adheres to the Epic coding standards. All contributions are governed by the terms of the EULA.

Next Steps

Now that you've downloaded and set-up Unreal Engine, you're ready to build the engine from source.

Footnotes

The first time you start the editor from a fresh source build, you may experience long load times. The engine is optimizing content for your platform to the derived data cache, and it should only happen once.

Your private forks of the Unreal Engine code are associated with your GitHub account permissions. If you unsubscribe or switch GitHub user names, you'll need to re-fork and upload your changes from a local copy.