EOSShared manages the loading of the SDK and prevents issues with dependency load order when multiple modules require the EOS SDK, there’s a similarly purposed module for Steam(the EOS OSS and the EOS voice chat module have a dependency on EOS).
Experimental is making Epic Staff experiments on their online service publicly available & visible.
OnlineFramework shares code for interacting with online gameplay services such as Lobby & Party, but also Login.
OnlineSubsystemNULL is the basic Unreal Engine online platform abstraction-subsystem, also known as LAN & Local.
OnlineSubsystemUtils is exposing some features of OnlineSubsystem to blueprints.
OnlineSubsystem and its interfaces provide a common way to access the functionality of online services such as Steam, Xbox Live, Facebook, and so on. When working on a game that ships on multiple platforms, or with support for multiple online services, the Online Subsystem ensures that the only changes developers need to make are configuration adjustments for each supported service.
Epic Online Services
OnlineSubsystemEOS (Epic Online Services) are free, cross-platform services created to enable fast, easy, and dependable high-quality game launching, operation, and scaling.
With a single SDK, we can help build a user-friendly ecosystem for both developers and users. Creators and developers benefit no matter how you choose to build and publish your games. Players can then play these games with friends across different platforms at the same quality experience. Our mission is to design the SDK to be as portable as possible to work on any engine, any store, and integrate with any major platform.
These services encompass both games services and can integrate with our Epic Account Services and Epic Games Store.
OnlineSubsystemSteam (Steamworks) enables you to ship Unreal Engine 4 (UE4) applications to Valve's Steam platform. The main purpose of the Steam module is to help you distribute your application with a set of features (such as matchmaking and leaderboards) to Steam users. Additionally, the Steam module implements several of the interfaces being exposed by the Online Subsystem, supporting most of what is offered by the Steamworks Software Development Kit (SDK).
VoiceChat is Epic Games selfmade voice chat service.