Godot Random Numbers: randi_range(), randf() and Seeds

Godot has random functions built in, with nothing to import:

var roll := randi_range(1, 6)            # 1, 2, 3, 4, 5 or 6
var speed := randf_range(80.0, 120.0)    # any float from 80 to 120
var chance := randf()                    # a float from 0 to 1
if randf() < 0.1:
	print("Critical hit!")               # about 10% of the time

randi_range() includes both ends. Godot 4 seeds the generator randomly at start, so every run of the game gives different numbers. You do not need randomize(), which Godot 3 required.

Repeatable Results with seed()

seed(number) restarts the sequence from a fixed point. The same seed always gives the same numbers, which is why the examples on this page print the same thing every time you run them:

extends Node

func _ready():
	seed(2026)
	for i in 5:
		print(randi_range(1, 6))

4
3
5
2
3

Seeds are how games make a daily challenge or a level that every player gets the same, and how you reproduce a bug that only happens with certain rolls.

Random Items, Shuffling and Positions

extends Node

func _ready():
	seed(2026)
	for i in 5:
		randi_range(1, 6)            # the same five rolls as above

	var deck := [1, 2, 3, 4, 5]
	deck.shuffle()                   # in place
	print(deck)

	var loot := ["coin", "gem", "potion", "key"]
	print(loot.pick_random(), " ", loot.pick_random())

[2, 4, 3, 1, 5]
key coin

A random point inside an area, for spawning, is two ranges:

var spawn := Vector2(randf_range(0, 1152), randf_range(0, 648))
var direction := Vector2.RIGHT.rotated(randf_range(0, TAU))   # any direction

RandomNumberGenerator

The functions above share one global generator. A RandomNumberGenerator is a separate generator with its own seed, so one system's rolls do not change another's:

extends Node

func _ready():
	var level_rng := RandomNumberGenerator.new()
	level_rng.seed = 123
	print(level_rng.randi_range(1, 100), " ", level_rng.randi_range(1, 100))

	var again := RandomNumberGenerator.new()
	again.seed = 123
	print(again.randi_range(1, 100), " ", again.randi_range(1, 100))

75 70
75 70

Give the level generator its own RNG and the map stays the same for a seed, even when combat rolls use the global one in between.

Weighted Random Drops

rand_weighted() picks an index with a chance in proportion to its weight. This drops common items often and rare ones seldom:

extends Node

func _ready():
	var rng := RandomNumberGenerator.new()
	rng.seed = 7
	var items := ["common", "rare", "legendary"]
	var weights := PackedFloat32Array([70, 25, 5])
	var counts := [0, 0, 0]
	for i in 1000:
		counts[rng.rand_weighted(weights)] += 1
	for i in items.size():
		print(items[i], ": ", counts[i])

common: 709
rare: 236
legendary: 55

Over 1,000 drops the counts land near 70%, 25% and 5%. The weights do not need to add up to 100.

Bell-Curve Values

randfn(mean, deviation) gives normally distributed floats: most results near the mean, few far away. It suits natural variation such as damage spread or the size of spawned rocks: rng.randfn(10.0, 2.0) is usually between 8 and 12.

Quick Reference