The GDExtension system
GDExtension is a Godot-specific technology that lets the engine interact with native shared libraries at runtime. You can use it to run native code without compiling it with the engine.
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GDExtension is not a scripting language and has no relation to GDScript.
This section describes how GDExtension works, and is generally aimed at people wanting to make a GDExtension from scratch, for example to create language bindings. If you want to use existing language bindings, please refer to other articles instead, such as the articles about C++ (godot-cpp) or one of the community-made ones.