Random

Random is a utility data pack for Minecraft 1.17+ that adds functions for random number generation and randomness-based predicates.

Functions

random:uniform

Generates a random number between $min and $max using a linear congruential generator. The generated value is saved to score $out random.

scoreboard players set $min random 0
scoreboard players set $max random 10
function random:uniform

Note: The resulting distribution is not truly uniform for values of $max-$min+1 that do not divide . While this is insignificant in almost all cases, random:true_uniform implements a method that counters modulo-induced bias.

random:binomial

Generates a random number following a binomial distribution given parameters $trials and $chance. The generated value is saved to score $out random.

scoreboard players set $trials random 5
scoreboard players set $chance 500000
function random:binomial

random:geometric

Generates a random number following a geometric distribution given parameter $chance, the probability of each Bernoulli trial with a scale of 1,000,000,000. The distribution is supported on {1, 2, 3, ...} The generated value is saved to score $out random.

scoreboard players set $chance 400000000
function random:geometric

random:poisson

Generates a random number using a Poisson distribution given the expected value lambda with a scale of 10. The generated value is saved to score $out random.

scoreboard players set $lambda random 20
function random:poisson

random:true_uniform

Generates a random number between $min and $max using a linear congruential generator and countering modulo-induced bias. The generated value is saved to score $out random. For low values of $min and $max, the bias is negligible and random:uniform should be used instead for efficiency.

scoreboard players set $min random 1
scoreboard players set $max random 1000000000
function random:true_uniform

random:number_provider

Generates a random number from storage using a syntax similar to number providers. type can be constant, uniform, binomial, geometric, or poisson. The minecraft namespace can optionally be used. Like vanilla number providers, type can be omitted if min/max or n/p are specified.

For type constant, the function will return the value of parameter value.

# Constant
data merge storage random:input {type: "constant", value: 5}
function random:number_provider

For type uniform, the function will return a random number between parameters min and max (inclusive). type is optional as long as min and max are specified.

# Uniform
data merge storage random:input {type: "uniform", min: 1, max: 6}
function random:number_provider

For type binomial, the function will return a random number following a binomial distribution with n trials of probability p. type is optional as long as n and p are specified.

# Binomial
data merge storage random:input {type: "binomial", n: 10, p: 0.166666667d}
function random:number_provider

For type geometric, the function will return a random number following a geometric distribution of parameter p.

# Geometric
data merge storage random:input {type: "geometric", p: 0.2d}
function random:number_provider

For type poisson, the function will return a Poisson variate of expected value lambda. Unlike random:poisson, no scale is expected for input.

# Poisson
data merge storage random:input {type: "poisson", lambda: 5.0f}
function random:number_provider

random:choose

Chooses a random tag from storage list random:input List and saves it to storage tag random:output Tag.

data modify storage random:input List set value ["green", "yellow", "orange", "pink"]
function random:choose
tellraw @a {"nbt": "Tag", "storage": "random:output"}

Predicates

random:coin_toss

Has a 50% chance of evaluating to true.

execute if predicate random:coin_toss run say hi!

# Simulating a coin toss
execute store result score <player> <objective> if predicate random:coin_toss
execute if score <player> <objective> matches 0 run say Heads
execute if score <player> <objective> matches 1 run say Tails

random:score_fraction

Succeeds with a probability of $a/$b.

scoreboard players set $a random 7
scoreboard players set $b random 12
execute if predicate:score_fraction run say 7/12

random:score_invert

Succeeds with a probability of 1/$chance.

scoreboard players set $chance random 6
execute if predicate random:score_invert run say 1/6

random:score_percentage

Succeeds with probability $chance in percents. At 0, the predicate always fails; at 100, it always succeeds.

scoreboard players set $chance random 5
execute if predicate random:score_percentage run say 5%

random:score_ppb

Succeeds with probability $chance in parts per billion. At 0, the predicate always fails; at 1,000,000,000, it always succeeds.

scoreboard players set $chance random 123456789
execute if predicate random:score_ppb run say 12.3456789%

Version

This data pack was designed for Minecraft: Java Edition 1.17 and works in 1.18 and 1.19 snapshots. The data pack format in pack.mcmeta is 10, but you can safely downgrade it to data pack formats used in previous game versions.

Some functions/predicates work in versions before 1.17:

Function	Supported versions
random:uniform	1.13+
random:binomial	1.17+
random:geometric	1.17+
random:poisson	1.13+
random:number_provider	1.15+, 1.17+ if type is binomial or geometric

Predicate	Version
random:coin_toss	1.15+
random:score_inverse	1.17+
random:score_percentage	1.17+
random:score_ppb	1.17+

Minecraft Random does not work in Minecraft: Bedrock Edition.