---
title: Modules
description: Group systems, bundles, resources, and messages into a generated module.
sidebar:
  order: 2
---

```csharp
[EcsModule]
[IncludeSystems(typeof(Motion))]
[IncludeBundle<Particle>]
[IncludeResource<FrameTime>]
public static partial class GameEcs;
```

`GameEcs.Module` is a generated `ModuleDescriptor`. A module includes the components, resources, and messages referenced by its included systems.

| Attribute | Effect |
| --- | --- |
| `IncludeSystems(typeof(T))` | Includes the systems declared on `T`. |
| `IncludeBundle<T>` | Includes a bundle. Required for bundles used by spawn commands. |
| `IncludeComponent<T>` | Registers an otherwise unused component. |
| `IncludeResource<T>` | Registers an otherwise unused resource. |
| `IncludeMessage<T>` | Registers an otherwise unused message type. |
| `IncludeModule(typeof(OtherModule))` | Includes another generated module. |
| `IncludeModule<T>` | The generic form, for module types that C# permits as generic arguments. |

## Cross-assembly modules

Generated modules expose versioned manifests for referenced assemblies, so a library can ship its own module and an application can include it. Compatible component and resource registrations share one world registration.

These cases fail validation:

- Registering the same named module twice.
- Conflicting component or resource metadata.
- Incompatible module ABIs.

## Runtime registration

The equivalent runtime API is `ModuleBuilder`, with `Component<T>`, `Tag<T>`, `Bundle<T>`, `Resource<T>`, `ManagedResource<T>`, `Message<T>`, `System`, and `Include` methods. `WorldBuilder` also accepts individual component, bundle, resource, managed-resource, and message registrations.