Gdextension

GDExtension

Run native C++ (or Rust) in Godot as a shared library without recompiling the engine. Use it for performance-critical code, wrapping existing C/C++ libraries, or language bindings.

Related skills: csharp-godot for when C# is enough, gdscript-advanced for GDScript performance idioms first, godot-optimization for profiling before going native, addon-development for distributing the result, export-pipeline for shipping the binaries.

1. When to reach for GDExtension

Reach for GDScript or C# for almost all game logic. Choose GDExtension only when you genuinely need it:

• Native speed in a hot loop that GDScript/C# can't keep up with (profile first — see godot-optimization).
• Wrapping a C/C++ library you must call directly.
• Building a language binding.

Contrast with C++ modules, which are compiled into the engine and therefore require shipping a custom engine binary. GDExtension's key advantage is that it runs against a stock Godot — you distribute just a shared library. It is "more complicated to use than GDScript and C#," so don't reach for it by default.

⚠️ Changed in Godot 4.7: Custom text servers are no longer a GDExtension use case — TextServer GDExtension build support was removed, so a custom TextServer must be compiled into the engine as a C++ module. See GH-117056.

2. Project & build setup

mkdir gdextension_example && cd gdextension_example
git init
# IMPORTANT: use the godot-cpp branch matching your target engine version (e.g. 4.3),
# not the literal "4.x".
git submodule add -b 4.3 https://github.com/godotengine/godot-cpp
cd godot-cpp && git submodule update --init && cd ..

Directory layout:

gdextension_example/
├── project/                # demo project to test the extension
│   └── bin/example.gdextension
├── godot-cpp/              # C++ bindings (submodule)
└── src/
    ├── register_types.{h,cpp}
    └── gdexample.{h,cpp}

Build with scons platform=<platform> (omit the platform to target the current one; default build is debug). The official SConstruct is a downloadable file from the C++ tutorial rather than hand-rolled here — follow godot-cpp's build docs. SCons is the official path; godot-cpp also supports CMake.

Godot 4.7+: Upstream's reference GDExtension interface files (e.g. gdextension_interface.h) now live in the godot-headers repository instead of godot-cpp (GH-115401). godot-cpp consumes them from there, so the submodule workflow above is unchanged — this only matters if you vendor the raw interface headers directly (e.g. for a custom language binding).

3. Binding a class (C++)

Header (gdexample.h):

#pragma once
#include <godot_cpp/classes/sprite2d.hpp>

namespace godot {
class GDExample : public Sprite2D {
    GDCLASS(GDExample, Sprite2D)
private:
    double time_passed = 0.0;
    double amplitude = 10.0;
    double speed = 1.0;
protected:
    static void _bind_methods();
public:
    void _process(double delta) override;
    void set_amplitude(double p_amplitude);
    double get_amplitude() const;
    void set_speed(double p_speed);
    double get_speed() const;
};
}

Bindings (gdexample.cpp — _bind_methods):

void GDExample::_bind_methods() {
    ClassDB::bind_method(D_METHOD("get_amplitude"), &GDExample::get_amplitude);
    ClassDB::bind_method(D_METHOD("set_amplitude", "p_amplitude"), &GDExample::set_amplitude);
    ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "amplitude"), "set_amplitude", "get_amplitude");

    ClassDB::bind_method(D_METHOD("get_speed"), &GDExample::get_speed);
    ClassDB::bind_method(D_METHOD("set_speed", "p_speed"), &GDExample::set_speed);
    ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "speed", PROPERTY_HINT_RANGE, "0,20,0.01"),
                 "set_speed", "get_speed");

    ADD_SIGNAL(MethodInfo("position_changed",
               PropertyInfo(Variant::OBJECT, "node"),
               PropertyInfo(Variant::VECTOR2, "new_pos")));
}

The patterns:

• GDCLASS(Class, Parent) — first line of every native class body; wires up the type into Godot's ClassDB.
• ClassDB::bind_method(D_METHOD("name", "arg"), &Class::method) — exposes a method (and names its arguments) so GDScript/C#/the editor can call it.
• ADD_PROPERTY(PropertyInfo(...), setter, getter) — registers an Inspector property; bind the getter and setter first, then reference them here by name.
• PROPERTY_HINT_RANGE with "0,20,0.01" turns the Inspector field into a slider (min, max, step).
• ADD_SIGNAL(MethodInfo("name", PropertyInfo(...), ...)) — declares a signal with typed arguments; emit it from code with emit_signal("position_changed", this, new_pos).

⚠️ Changed in Godot 4.7: The GDExtension interface functions object_cast_to and classdb_get_class_tag are deprecated in favor of is_class-based casts. Binding libraries (godot-cpp, gdext) handle this internally — but native code that calls these interface functions directly should migrate its cast paths. See GH-119254.

4. Entry point & the .gdextension file

Entry point (register_types.cpp):

void initialize_example_module(ModuleInitializationLevel p_level) {
    if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) return;
    GDREGISTER_CLASS(GDExample);
}
void uninitialize_example_module(ModuleInitializationLevel p_level) {
    if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) return;
}
extern "C" {
GDExtensionBool GDE_EXPORT example_library_init(
    GDExtensionInterfaceGetProcAddress p_get_proc_address,
    const GDExtensionClassLibraryPtr p_library,
    GDExtensionInitialization *r_initialization) {
    godot::GDExtensionBinding::InitObject init_obj(p_get_proc_address, p_library, r_initialization);
    init_obj.register_initializer(initialize_example_module);
    init_obj.register_terminator(uninitialize_example_module);
    init_obj.set_minimum_library_initialization_level(MODULE_INITIALIZATION_LEVEL_SCENE);
    return init_obj.init();
}
}

The .gdextension file (project/bin/example.gdextension):

[configuration]
entry_symbol = "example_library_init"
compatibility_minimum = "4.3"
reloadable = true

[libraries]
macos.debug = "res://bin/libgdexample.macos.template_debug.dylib"
macos.release = "res://bin/libgdexample.macos.template_release.dylib"
windows.debug.x86_64 = "res://bin/gdexample.windows.template_debug.x86_64.dll"
windows.release.x86_64 = "res://bin/gdexample.windows.template_release.x86_64.dll"
linux.debug.x86_64 = "res://bin/libgdexample.linux.template_debug.x86_64.so"
linux.release.x86_64 = "res://bin/libgdexample.linux.template_release.x86_64.so"

The exported extern "C" symbol name must equal entry_symbol, or the extension won't load. Register classes with GDREGISTER_CLASS, gated on MODULE_INITIALIZATION_LEVEL_SCENE. The [libraries] keys are platform.feature.arch tags; template_debug / template_release distinguish build configs. Optional sections: [icons] (per-node editor icon) and [dependencies] (extra libs copied on export).

Godot 4.7+: The raw GDExtension interface adds refcount-aware construction and registration entry points — classdb_construct_object3 and classdb_register_extension_class6 (GH-118214). Binding libraries built against 4.7 headers use them automatically; they only concern code that calls the interface directly.