At Epic, we’re deeply passionate about creativity, and mods are a huge platform for unlocking the ability for creators of all types to realize their ideas. Unreal Engine 4 is built in a way that allows game developers to easily afford their players the ability to be part of the creative process. We’re no stranger to the importance of mods or mod culture and are completely stoked to provide the option for UE4 projects of all types to be moddable.
So what are the details? Let’s start with the F.A.Q.s.
Does UE4 support moddable games?
Yes! Unreal Engine 4 has been designed with modding in mind. The complete source code, easy-to-use tools, and great tutorials and documentation we provide to you for developing your games are also available to your game’s modding community to take full advantage of! We’ve also designed Unreal Engine 4’s business terms to be friendly to modding.
Why are mods interesting?
An active mod community can take a game far beyond the scale and scope that a developer can achieve alone, and have a multiplicative effect on the game’s community engagement and success. Many of us at Epic got our start in the mod communities surrounding early games like Quake, Unreal and Half-Life, and now we’re proud to provide tools and business terms enabling game developers to take modding to the next level!
As a developer of a moddable game, what can I redistribute?
First of all, you can redistribute your game, and mods for your game, to anyone and through any channels you desire. These redistribution rights are covered in the EULA section 1a.
Second, you can redistribute your customized version of the Unreal Editor, and (if you choose) UE4 source code, freely, to the Unreal Engine 4 community through Epic’s UE4 channels including GitHub and the Marketplace. These redistribution rights are covered in EULA section 1b.
Why does the Unreal Editor and source have to be released through Epic’s UE4 channels?
The intent here is to keep the entire Unreal Engine developer community together, so that everyone from pros to indies and modders shares the same documentation, forums, content marketplace, and collaboration resources. Over time we’ll be doing a lot to expand this and further improve the engine for moddable games here.
How should I distribute the editor to mod developers?
Create a GitHub fork of Epic’s UE4 repository and place your editor binaries there, and create a tutorial page telling users how to install it into their existing installation of your game and get started. In time, we’ll provide a more user-friendly means of distributing binaries.
Can I distribute C++ source to mod developers (and should I)?
You’re free to redistribute all of Epic’s UE4 source, and your modifications and extensions to it, to the UE4 community, through a fork of Epic’s UE4 GitHub repository. Of course, you’re also free to not redistribute any source, if that’s what you prefer.
Generally, source code is of interest to a smaller and more hardcore developer community than the Unreal Editor and its user-friendly interface for Blueprint visual scripting and other systems. We recommend starting with a release of mod tools, and considering source later as your community gains momentum.
Are there any restrictions on how I can distribute mods for my game?
No. As a game developer, you can distribute your game’s mods through any channels you like, and you can give mod makers permission to distribute their mods through whatever channels you choose. Mods can be distributed directly to your customers online, or through a publisher, or through services such as Valve’s Steam Workshop.
Can mods be sold?
It is up to the developer of each moddable UE4-based game to decide whether and how mods may be sold for that game. If the game developer chooses to control the curation and sale of mods to users, then the EULA’s royalty terms (section 4) apply to the game developer’s revenue. If the game developer allows mod developers to sell their own mods directly to users, then those terms apply to the mod developer’s revenue.
Can assets be used from the UE4 Marketplace for mod development?
Yes, mod developers are free to purchase UE4 Marketplace content for use in their mods, and to redistribute that content to the general public as part of their playable mods (in the form of object code and cooked content).
However, mod developers may only share commercial Marketplace content in source code or uncooked form within their mod development team. This content format mustn’t be released to the community at large, as Marketplace developers are relying on selling it to earn their livings.
Where can I find support for making mods using UE4?
Moddable games will generally include a tutorial on the specifics of modding their game. Beyond that, all of Unreal Engine 4’s documentation and tutorial videos are generally applicable to all moddable games build in UE4. There’s a wealth of information on https://docs.unrealengine.com/latest/INT/ and check out the light-weight abstraction of many UGC features built for Robo Recall and the Robo Recall Mod Kit as a plugin, as well as an example project to show how it all works!
Have further questions? Let us know!