Modules

Godot's modules/ directory holds optional engine extensions that can be enabled or disabled at compile time. They are not "modules" in the OS dynamic-linking sense — they compile into the same binary as the rest of the engine and register themselves through register_module_types. Disabling a module via module_<name>_enabled=no (or the custom_modules mechanism) drops its code entirely from the build.

Why modules exist

Several distinct reasons:

1. Optional features that not every project needs (Mono/C#, MP3 decoding, OpenXR, regex).
2. Pluggable backends (godot_physics_3d vs jolt_physics, text_server_adv vs text_server_fb, navigation_3d) where the user picks one.
3. First-party importers that do not belong in core/ (glTF, FBX, ZIP).
4. Format support for media types (Vorbis, Theora, WebP, KTX, DDS, BMP, JPEG, HDR, TGA, SVG).
5. Hosted scripting languages (gdscript, mono).

Most modules are enabled by default. The mono module is the most prominent opt-in.

In-tree modules

Module	Purpose	One-line
GDScript	Built-in dynamic language	Lexer, parser, analyzer, compiler, VM, debugger, LSP
Mono / C#	C# scripting via .NET 8	Hostfxr, generated bindings, marshalling glue
glTF	glTF 2.0 import/export	First-class 3D scene format
Jolt Physics	Recommended 3D physics	Wraps Jorrit Rouwe's Jolt library
OpenXR	Primary XR runtime	Action sets, hand/face/body tracking, layers
Multiplayer	High-level networking	RPC, scene replication, peer abstractions
Other modules	Format/effect/utility modules	Audio formats, regex, noise, CSG, visual shader, …
text_server_adv	Default text server	HarfBuzz + ICU + FreeType
text_server_fb	Fallback text server	FreeType only
godot_physics_2d / godot_physics_3d	Built-in physics backends	SAT/GJK/EPA + iterative solver
navigation_2d / navigation_3d	Default navigation backends	Recast + RVO2
webrtc, websocket, enet, upnp, mbedtls	Networking	TLS, ENet, WS, WebRTC, UPnP discovery
webxr	WebXR backend	Web platform only
mobile_vr	Phone-stereo VR	Cardboard-style
gridmap	3D tile system	GridMap node, MeshLibrary resources
csg	Constructive solid geometry	Brushes, booleans, level prototyping
visual_shader	Visual shader graphs	Drag-and-drop shader authoring
lightmapper_rd	RD-based lightmap baker	Computes static GI for LightmapGI
regex	PCRE2 regex API	RegEx/RegExMatch classes
noise	Noise generators	FastNoiseLite, NoiseTexture2D, NoiseTexture3D
mp3, vorbis, ogg, theora	Media decoders	Audio + video
webp, svg, jpg, bmp, dds, hdr, ktx, tga, tinyexr	Image format loaders	Decoders for textures
basis_universal, astcenc, betsy, bcdec, cvtt, etcpak	Texture compressors	Per-format compressed texture pipelines
meshoptimizer, xatlas_unwrap, vhacd	Mesh tooling	Index/vertex optimization, UV atlasing, convex decomposition
interactive_music	Layered/transitioning music	AudioStreamInteractive, AudioStreamSynchronized
objectdb_profiler	Object DB profiler	Editor-only insight into live Object counts
jsonrpc	JSON-RPC 2.0	Used by the GDScript LSP and editor remote tools
raycast	Embree-backed raycasting	Used by lightmapper + navigation
freetype, glslang, msdfgen	Library wrappers	Vendored thirdparty registered via small modules
zip	Zip archive support	Reading + writing
accesskit	Accessibility integration	Cross-platform a11y via AccessKit

A module's structure is conventional:

modules/<name>/
├── config.py              Build-time options + can_build callback
├── SCsub                  SCons enumeration of sources
├── register_types.{cpp,h} Module entry: registers classes/services with engine
├── doc_classes/           XML class reference for the module's classes
├── icons/                 Editor icons (SVG)
├── editor/                (optional) Editor plugins this module ships
├── tests/                 (optional) doctest unit tests
└── …source code…

Some modules also vendor third-party code under thirdparty/ at the repo root (e.g., HarfBuzz, ICU, FreeType, Jolt, Mbed TLS, Vulkan-Loader). The vendoring keeps build reproducibility and removes the need for git submodules.

Disabling and replacing

scons module_<name>_enabled=no disables a module. The build emits modules_enabled.gen.h listing the active set; #ifdef MODULE_<NAME>_ENABLED guards code in other layers.

External modules can be added via custom_modules=path/to/module1,path/to/module2 — useful for proprietary integrations.