A platform-agnostic online layer — identity, sessions, friends, presence, parties, achievements, stats, leaderboards, store, purchases, entitlements, voice, and cloud save behind one typed, Blueprint-friendly subsystem.
Online · Multiplayer · Unreal Engine 5
Ship on Steam, EOS, and consoles, from one online API.
CrimsonOnlineSubsystem wraps Epic's OnlineSubsystem behind a typed, Blueprint-friendly GameInstance subsystem. One UCrimsonOnlineSubsystemGI owns 15 specialised services — identity, sessions, friends, presence, parties, achievements, leaderboards, raw stats, store, purchases, entitlements, user info, voice, external UI, and cloud save. The platform is detected at boot, and a DebugPlatformOverride lets you test any platform in PIE without relaunching.
Why CrimsonOnlineSubsystem
Write your online code once against typed services — the right platform backend is resolved at boot.
One subsystem, 15 typed services
UCrimsonOnlineSubsystemGI owns one specialised service object per OSS interface and exposes each through a strongly-typed accessor — GetSessionService(), GetFriendsService(), GetStoreService(), and twelve more. Never null after initialisation, so your game code stops sprinkling interface-validity checks everywhere.
Six platforms, zero rewrites
Steam, Epic Online Services, PlayStation Network, Xbox / GDK, Nintendo Switch, and a Null backend for LAN development — each mapped to its OSS module. Platform detection happens once at boot (GetActivePlatform()), and your calls stay identical across all of them.
Sessions without the boilerplate
FCrimsonSessionSettings configures a session in one struct — player counts, LAN, invites, presence, plus arbitrary CustomSettings for search filters. Create, find, join, update, and destroy through typed calls with lifecycle delegates, then travel with GetResolvedConnectString.
The whole social stack
Friends, presence, and parties as first-class services: read and refresh the platform friend list into FCrimsonFriendInfo, publish rich presence, create parties, invite, kick, and transfer leadership — with delegates like OnInviteReceived and OnPartyMemberJoined driving your UI.
Achievements, stats & leaderboards
Write achievement progress 0–100 and let the platform unlock at 100. Submit ranked scores to global leaderboards, read ranges or friends-only slices, and track raw per-player stats with Sum / Set / Largest / Smallest write semantics — two stats services, clearly separated.
Store, DLC & cloud save
Query storefront offers, open the platform checkout, verify receipts, and check ownership through the entitlement service. A DataTable-based DLC mapping resolves one internal FName to the right Steam App ID, EOS offer, PSN, Xbox, or Switch product — and cloud save handles per-player file blobs.
A closer look
Host, browse, join — a session flow designers can wire
Log in with the Async Login Blueprint node, create a session from an FCrimsonSessionSettings struct, and populate a server browser straight from the OnFindSessionsComplete results — each FCrimsonSessionSearchResult carries ping and your custom filter values. Join, resolve the connect string, travel. Every step is a typed call with a completion delegate.
Friends, presence, and parties in one pass
Read the platform friend list once and render it from FCrimsonFriendInfo — display name, condensed presence state, rich presence text, and whether they're in your game. Send and answer invites, then move the group into a party: create, invite, join, kick, and transfer leadership, with delegates keeping every member's UI in sync.
Test every platform without leaving PIE
Set DebugPlatformOverride in Project Settings and the subsystem behaves like Steam, EOS, or a console right inside PIE — no relaunch, no special build. The Null backend gives you LAN sessions with no auth for day-one development, bVerboseLogging prints every OSS callback result, and the crimson.online.get_state MCP tool reports live subsystem state to your AI tooling.
Technical details
- Engine
- UE 5.8
- Platforms
- Windows, Mac, Linux
- Blueprint-ready
- Yes
- C++ required
- No
- Network replicated
- No
- Dependencies
- CrimsonCommon, OnlineSubsystem, OnlineSubsystemUtils
- Last updated
- June 2026
Frequently asked questions
Which online backends does it support?
OnlineSubsystemSteam), Epic Online Services (OnlineSubsystemEOS), PlayStation Network, Xbox / GDK (OnlineSubsystemLive), Nintendo Switch, and the Null backend for LAN-only development. All six include DLC-identifier resolution through the mapping table; the Null backend is sessions-only with no auth, by design.Do I need C++ to use it?
.uproject or .Build.cs edits — and flows like login run through async Blueprint nodes such as Async Login. C++ teams get the same 15 services through strongly-typed accessors on UCrimsonOnlineSubsystemGI.Does it work in multiplayer?
Does it depend on other Crimson plugins?
OnlineSubsystem and OnlineSubsystemUtils modules plus whichever platform OSS module you ship with — no other Crimson plugin required.How does it relate to the free CrimsonCommon foundation?
Go online without marrying a platform
Enable the plugin, point DefaultEngine.ini at your backend, and log in with one async node. The same session, social, progression, and store code then ships everywhere your game does.
Pricing
CrimsonOnlineSubsystem is sold on Fab under Epic’s two standard licenses — both include the full plugin, source, and updates.
Completes your setup
Built on the free CrimsonCommon foundation, so it pairs cleanly with the rest of the suite:
Fragment-based saving — each system owns its own data.
- Independent Fragments
- No Cross-Plugin Coupling
- Blueprint-Ready
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