Patching Overview

Once you have released your project, you might want to make updates to it after the initial release. This process is known as patching. Patching usually includes new content that addresses known issues, or that fixes vulnerabilities in the original release. Technically, patching also includes Downloadable Content (DLC) that extends the original release. However, we cover DLC in separate documentation.

Different Methods for Patching

There are several methods for creating patches, but they all use one of two approaches. One approach keeps files from the original release or previous patches, but adds a pointer to new content. The other approach is to compare content in the original build with content from the patch--this approach only downloads new content.

While you can build patches in Unreal Engine 4, we do not support distribution of patches for your project. Distribution varies by platform, and must be accomplished using each platform’s SDK.

Installing a Patch

The patching process creates a .pak file in [ProjectName]\Saved\StagedBuilds[PlatformName][ProjectName]\Content\Paks. This .pak file is the patch that should be distributed to users. For example, on Windows, you would create an installer to copy that .pak file into the user's [ProjectName]\Releases[VersionNumber][PlatformName] folder, next to the original content .pak file.

The patch .pak file will automatically be mounted if it is located in any of the .pak search directories set for your device in FPakPlatformFile::GetPakFolders. To prioritize patches, the mounting system uses a _p at the end of the filename to determine that it gets priority over other .pak files. It can be renamed, but you need to include the _p.pak at the end of the file name.

If you build two patches from the same release version, they are both complete patches. Remove the first patch before installing the second patch.