Variables

A variable is a name that holds a value. Variable values can be numbers, strings, booleans, data types, and more.

Name variables

Variable names can be any non-reserved string of letters, digits, and underscores that don't start with a digit.

LETTERS   -- valid
a1        -- valid
var_name  -- valid
_test     -- valid

if        -- NOT valid
25th      -- NOT valid

Variable names are case-sensitive, so TestVar and TESTVAR are different names. Avoid naming variables with an underscore and all uppercase letters, such as _VERSION, because Luau may reserve them for internal global variables.

Best practices

It's best practice to spell out words fully. Abbreviations generally make code easier to write, but harder to read. Following common naming practices when naming your variables can help you and others understand their meaning or purpose:

• Use PascalCase names for class and enum-like objects.
• Use PascalCase names for all Roblox APIs. camelCase APIs are mostly deprecated.
• Use camelCase names for local variables, member values, and functions.
• Use LOUD_SNAKE_CASE names for constants, such as const values or other values that you don't expect to change.
• Don't capitalize entire acronyms within names. For example, write aJsonVariable or MakeHttpCall.

Reserved names

Luau reserves the following keywords, so you can't use them to name variables or functions:

• and
• for
• or
• break
• function
• repeat
• do
• if
• return
• else
• in
• then
• elseif
• local
• true
• end
• nil
• until
• false
• not
• while

Assign values

To create a variable and assign a value to it, use the = operator. Put the variable on the left of the = and the value on the right. If you don't put a value, the value is nil.

Variables can have global or local scopes. They have global scope by default, but it's almost always better to create them with local scope because Luau accesses local variables faster than global ones. To give a variable local scope, put the keyword local before a variable's name when you assign a value to it. To give it local scope and also prevent reassigning it, use const instead of local. For more information, see Scope.

local nilVar
local x = 10
local word = "Hello"
local boolean = true

print(nilVar) -- nil
print(x) -- 10
print(word) -- Hello
print(boolean) -- true

Assign values to multiple variables

You can assign values to multiple variables in one line by separating each variable-value pair with a comma. If you have more variables than values, then Luau assigns nil to the extra variables. If you have more values than variables, Luau doesn't assign the extra values to any variables.

local a, b, c = 1, 2, 3
local d, e, f = 4, 5 -- extra variable
local g, h = 7, 8, 9 -- extra value

print(a, b, c) -- 1, 2, 3
print(d, e, f) -- 4, 5, nil
print(g, h) -- 7, 8

Change values

To change a value of a variable, assign another value to it.

local x, y = 10, 20
print(x) -- 10
print(y) -- 20

x = 1000
y = 2000
print(x) -- 1000
print(y) -- 2000

Const variables

To create a variable that you can't reassign, use const instead of local. Trying to reassign a const variable causes an error, including through a compound assignment operator such as +=.

const MAX_HEALTH = 100

MAX_HEALTH = 50 -- error: cannot reassign a const variable
MAX_HEALTH += 1 -- error: cannot reassign a const variable

Like local, const accepts a type annotation, such as const MAX_HEALTH: number = 100.

You can also declare a function with const, which prevents reassigning the name of the function.

const function addOneAndTwo()
	local result = 1 + 2
	print(result)
end

addOneAndTwo = nil -- error: cannot reassign a const variable

const makes the variable itself immutable, not the value that it holds. If a const variable holds a table, you can still change the contents of the table. To make the contents immutable as well, use table.freeze().

const SETTINGS = { volume = 0 }

SETTINGS.volume = 1 -- ok, changes a value inside the table
SETTINGS = {} -- error: cannot reassign a const variable

Unlike the keywords in Reserved names, const is contextual. Luau only treats it as a keyword where local is valid, so existing code that uses const as a variable name still works.

local const = 1
print(const) -- 1

const = 2 -- ok, `const` is a variable name here

For more information and edge cases, see the Luau documentation.