The free foundation the entire Crimson suite is built on.
Free · Foundation · Unreal Engine 5
One foundation. Every plugin builds on it — none depend on each other.
CrimsonCommon is the shared contract layer for the suite: replicated tag stacks, a tag-routed message bus, cross-plugin ability sets, the CommonUI layer system, and Game-Feature-ready base classes — so you enable only the plugins you want and they still cooperate.
Why CrimsonCommon
One shared layer holds the contracts and utilities every Crimson plugin agrees on.
The Cardinal Rule
No Crimson plugin depends on another — only on Common. Plugins talk through shared interfaces, so you enable just what you need and everything still cooperates.
Modular base classes
Game-Feature-extensible Character, Pawn, Controller, State, GameMode/State, and AI bases. Reparent once and Game Features can attach components and abilities at runtime — it replaces ModularGameplayActors.
Replicated tag stacks
FCrimsonTagStackContainer stores (tag → count) on a FastArray and delta-replicates only what changed — ammo, charges, currencies, buildup. Dirtying is handled for you.
Cross-plugin ability sets
Bundle abilities, effects, and attributes into a CrimsonAbilitySet, then grant and revoke it across plugin boundaries through an interface — with no dependency on the GAS plugin.
Tag-routed message bus
UCrimsonMessageSubsystem broadcasts struct-typed events on gameplay-tag channels. Sender and receiver never reference each other — a dependency-free GameplayMessageSubsystem.
CommonUI foundation
A primary game layout, layer stack, and UI extension points, plus the login/session layer. Folds CommonGame and CommonUser into one layer you depend on.
A closer look
Enable it once, build on it forever
Tick CrimsonCommon in Edit → Plugins and restart. Blueprint projects need nothing else; C++ projects add one module line. From then on it's an implicit dependency — enabling any other Crimson plugin pulls it in automatically.
Decouple plugins with contracts, not includes
When two systems must talk, the interface lives in CrimsonCommon and each side talks to the contract — never to the other plugin. Equipment can grant a weapon's abilities without ever including the ability-system plugin.
Adopt incrementally — it's a toolbox, not a pipeline
Every piece is independent and opt-in. Reparent the Character today and the Player State later; use tag stacks without touching the message bus. Take only what your game needs.
Technical details
- Engine
- UE 5.8
- Platforms
- Windows, Mac, Linux
- Blueprint-ready
- Yes
- C++ required
- No
- Network replicated
- Yes
- Dependencies
- GameplayAbilities, ModularGameplay, EnhancedInput, CommonUI, OnlineSubsystem
- Last updated
- June 2026
Frequently asked questions
Is it really free?
Do I need C++ to use it?
CRIMSON_LOG_* macros are the one C++-only feature.Does it depend on other Crimson plugins?
Will adopting it change how my game runs?
What does it replace?
Start with the foundation
CrimsonCommon is free and takes minutes to adopt. Enable it, swap in the modular base classes, and you're ready for the rest of the suite.
Ready for more? Add a premium system
You're already on the Crimson foundation — these paid systems drop straight in, no glue code.
Replicated, GAS-native skill trees with a two-graph editor.
- Two-Graph Editor
- Material Splines
- Server-Authoritative
- Atomic Respec & Loadouts
A full Gameplay Ability System layer for UE5.
- Custom ASC & Abilities
- Slot-Based Augments
- Modifiers & Phases
- Graph-Based Combos
Layout-agnostic, fully replicated inventory and crafting.
- Pluggable Topology
- Runtime Constraints
- Scoped Containers
- Crafting
- No RPCs to Write