attempt to index number with 'X'

What the message means

ServerScriptService.CoinPad:7: attempt to index number with 'Value'

Other forms of the same message:

• attempt to index boolean with 'Parent'
• attempt to index number with 'Transparency'

Numbers and booleans are plain values. They have no children and no properties, so 5.Value or true.Parent has nothing to read. Luau names the type it found (number, boolean) and the key you asked for.

Strings behave differently: reading an unknown name from a string gives nil without an error, so a mistake with a string shows up one step later as attempt to index nil or attempt to call a nil value.

Causes and fixes

Three things cause this error in practice. Each one below has the smallest code that triggers it, then the fix.

• You read .Value, then used it like the object
• The ipairs variables are the wrong way round
• A true or false went where an object should be

You read .Value, then used it like the object

coins.Value is a number. If you save it in a variable and later write coins.Value again on that number, you get attempt to index number with 'Value'. Saving the number also means changing the variable never changes the real stat.

local Players = game:GetService("Players")

Players.PlayerAdded:Connect(function(player)
	local leaderstats = player:WaitForChild("leaderstats")
	local coins = leaderstats:WaitForChild("Coins").Value -- a number
	-- attempt to index number with 'Value'
	coins.Value += 10
end)

Keep the object (the IntValue) in the variable, and read or change .Value on it when you need it.

local Players = game:GetService("Players")

Players.PlayerAdded:Connect(function(player: Player)
	local leaderstats = player:WaitForChild("leaderstats", 10)
	local coins = leaderstats and leaderstats:WaitForChild("Coins", 10)
	if coins and coins:IsA("IntValue") then
		coins.Value += 10 -- changes the stat itself
	end
end)

The ipairs variables are the wrong way round

ipairs gives the position first and the value second. Writing for part, i in ipairs(list) makes part the number 1, 2, 3, and the first dot on it fails.

local folder = workspace:WaitForChild("Lights")

for light, i in ipairs(folder:GetChildren()) do
	-- light is the index (a number): attempt to index number with 'Transparency'
	light.Transparency = 0.5
end

Put the index first. Use _ when you do not need it, and check the class before setting a property only some objects have.

local folder = workspace:WaitForChild("Lights")

for _, light in ipairs(folder:GetChildren()) do
	if light:IsA("BasePart") then
		light.Transparency = 0.5
	end
end

A true or false went where an object should be

Functions like IsA, IsDescendantOf and comparisons return true or false, not the object. Using that result with a dot gives attempt to index boolean with. The same happens with x == y and x style shortcuts written the wrong way round.

local part = script.Parent

part.Touched:Connect(function(hit)
	local isCharacterPart = hit.Parent:FindFirstChild("Humanoid") ~= nil
	-- a boolean: attempt to index boolean with 'Parent'
	print(isCharacterPart.Parent.Name)
end)

Keep the object and the check in separate variables: the object to use, the boolean only in the if.

local part = script.Parent :: BasePart

part.Touched:Connect(function(hit: BasePart)
	local character = hit:FindFirstAncestorOfClass("Model")
	local humanoid = character and character:FindFirstChildOfClass("Humanoid")
	if character and humanoid then
		print(character.Name)
	end
end)

How to find the line that causes it

1. Open Output (Window menu, or the Script tab), clear it with Ctrl+K (⌘K on Mac), and press Play.
2. Find the first red line. It starts with the script's place in the Explorer and the line number, such as ServerScriptService.Shop:12:.
3. Click the red line. Studio opens that script with the cursor on the failing line.
4. Read the lines between Stack Begin and Stack End under it: they list the calls that led there, newest first, so you can see which function called the broken one.
5. Still not sure which value is wrong? Add print(typeof(x), x) just above the line, or set a breakpoint on it and read the values in the Watch window.

Questions

Sources and further reading

• Roblox Creator Docs: IntValue
• Roblox Creator Docs: ipairs. returns the index, then the value
• Luau: syntax

How the code was checked: every block marked Fixed passes Luau's strict type checker against Roblox's API definitions (luau-lsp, 23 October 2026), and every block marked Breaks compiles and fails only when it runs. The message wording was checked by running the broken code with the Luau command line tool and against the message strings in Roblox Studio itself on 23 October 2026. A type check catches misspelt APIs and wrong types, not game logic, so playtest in Studio before you publish.