Migrate Godot Projects to Version 4

Godot 4 Migration Guide explains major changes developers encounter when moving a Godot 3.x project to Godot 4. It focuses on GDScript 2.0 syntax, the replacement Tween workflow, and export annotations, while also covering property definitions, signal connections, typed arrays, and awaiting signals. The examples pair older forms with their Godot 4 counterparts so a specific upgrade error can be traced to the relevant language or API change.

Annotations replace several older keywords: export variables become @export variables, onready becomes @onready, and tool becomes @tool at the top of the file. Properties define setters and getters inline rather than relying on setget references. The illustrated health property combines a typed value, setter behavior, getter behavior, and a change signal.

Use it when porting a Godot 3 project, fixing syntax errors after upgrading, replacing deprecated nodes, or revising exported variables. Begin in a backed-up branch or copy, select an exact Godot 4 version, and validate conversion before changing files.

Do not replace the working Godot 3 build solely because scripts compile. Inspect converter gaps, renamed nodes, shaders, physics behavior, plugins, and export targets, then test scenes and saved games. Treat the examples as fragments for an appropriate Node script; the Enemy example requires a declared project type. Static typing supports clearer contracts and type checking, but performance should be measured in the actual engine and workload.

Inputs are the existing project, the selected target engine version, and the scripts or upgrade errors being addressed. Outputs are revised script patterns and migration checks for the affected behavior. The Godot 3 Tween scene node is replaced by a Tween object created through create_tween(). The example animates sprite position and starts a parallel opacity animation:

var tween = create_tween()
tween.tween_property($Sprite, "position", Vector2(100, 100), 1.0)
tween.parallel().tween_property($Sprite, "modulate:a", 0.0, 1.0)

Signal connections move toward callables, and direct signal-object emission is preferred where available. Coroutines replace yield with await on the signal being awaited. Typed arrays make element expectations explicit while collecting matching children. Inspector annotations such as @export_range and @export_file provide more specific editing controls.

Parent methods are called with super() rather than the older dotted function form. For Tween type errors, the guide clarifies that the result is a Tween object returned in a Node context, not a scene node or a SceneTreeTween type. These individual changes still need validation within the converted project.