JSON vs ConfigFile vs Resource in Godot 4 — which save format and when

Godot 4 gives you three sanctioned ways to write a save file, and the docs describe each one without ever telling you which to pick. So you pick the first one you read about, ship it, and discover the trade-off six months later when a player's Vector2 comes back as a Dictionary or an old save crashes the new build. Here's what each format actually costs.

JSON: portable, readable, type-lossy

FileAccess plus JSON is the path most tutorials take, because it's the one that looks like saving in every other language.

func save_game(data: Dictionary) -> void:
    var f := FileAccess.open("user://save.json", FileAccess.WRITE)
    f.store_string(JSON.stringify(data, "\t"))

func load_game() -> Dictionary:
    if not FileAccess.file_exists("user://save.json"):
        return {}
    var f := FileAccess.open("user://save.json", FileAccess.READ)
    var parsed = JSON.parse_string(f.get_as_text())
    return parsed if parsed is Dictionary else {}

The catch is that JSON has no idea what a Godot type is. It knows objects, arrays, strings, numbers, booleans and null — that's the whole list. Three consequences bite in practice:

• Numbers come back as floats. Save level = 3, load 3.0. Anything you feed to an array index or a match on an int needs an explicit int() on the way out.
• Dictionary keys become strings. {1: "sword"} saves and loads as {"1": "sword"}. Inventory slots keyed by int are the usual victim.
• Vector2, Color and friends don't survive. You convert them by hand going in and coming out, every field, forever.

What you get in exchange is real: the file is plain text any tool can read, nothing in it can execute, and you can parse it outside Godot — a web leaderboard, a Python script, a save editor you write in an afternoon.

ConfigFile: Variants that round-trip, in an INI file

ConfigFile stores sections and keys, and it keeps Godot's own types.

func save_game() -> void:
    var cfg := ConfigFile.new()
    cfg.set_value("player", "position", Vector2(120, 48))
    cfg.set_value("player", "hp", 3)
    cfg.set_value("world", "unlocked", ["cave", "ridge"])
    cfg.save("user://save.cfg")

func load_game() -> void:
    var cfg := ConfigFile.new()
    if cfg.load("user://save.cfg") != OK:
        return
    var pos: Vector2 = cfg.get_value("player", "position", Vector2.ZERO)
    var hp: int = cfg.get_value("player", "hp", 3)

Vector2 goes in and Vector2 comes out. 3 stays an int. Arrays and Dictionaries of Variants work too, and get_value() takes a default as its third argument — which quietly solves the "player has an old save without this key" problem that forces try/except gymnastics in JSON.

The limits: it stores Variants, not objects, so a custom class instance isn't going in. It's flat by nature — two levels, section and key — so deeply nested state gets encoded as one big Dictionary value and you've lost the readability you came for. And the format is Godot's own, so nothing outside the engine parses it for free.

Resource: typed, autocompleted, and the one with a security warning

A custom Resource turns your save into a class with real fields.

class_name SaveData extends Resource

@export var hp: int = 3
@export var position: Vector2 = Vector2.ZERO
@export var unlocked: Array[String] = []

func save_game(data: SaveData) -> void:
    ResourceSaver.save(data, "user://save.tres")

func load_game() -> SaveData:
    if not ResourceLoader.exists("user://save.tres"):
        return SaveData.new()
    return load("user://save.tres") as SaveData

Typos become editor errors instead of runtime nils, and you get autocomplete on your own save. It is by far the nicest to write.

Two things to know before you ship it. First, resource files can reference scripts, and loading one runs them — the Godot docs say outright not to load resources from untrusted sources. A save file in user:// is a file the player (or anything else on their machine) can swap. If your game ever accepts a save from elsewhere — cloud sync, a Discord "try my seed", a modding scene — that's a code-execution path, not just a cheating one. Second, the file is tied to your script: rename the class, move the file, or drop an @export and old saves stop loading cleanly.

The comparison

One honest note on that last row: the key ships inside your game binary, so encryption here stops casual editing, not a determined player.

The rule

Shipping a single-player game and you want the least future pain? ConfigFile. It round-trips Godot's types, defaults are built in, and nothing in it can run.

Anything outside Godot ever reads the save — a server, a stats page, a tool? JSON, and pay the type-casting tax deliberately.

Prototype or jam, all internal, speed is everything? Resource. Just know you'll want to move off it before you accept a save file you didn't write.

Whichever you pick, the format is the easy half. The half that shows up later is versioning old saves into a new schema, not corrupting the file when the game is killed mid-write, and keeping a backup to fall back on. Saltmire Save is the paid tool I built after writing that layer one time too many: one-line save and load, plus schema migration, backup recovery, gzip compression and encryption — MIT licensed, so you can read exactly how it handles each of these.