attempt to compare nil < number

What the message means

ServerScriptService.Shop:18: attempt to compare nil < number

Other forms of the same message:

• attempt to compare number < nil
• attempt to compare string < number
• attempt to compare nil <= number
• attempt to compare Instance < number

Luau turns a > b into b < a before it runs it. That is why the message can list the sides in the opposite order from your code: read it as "one side was nil, the other a number", then check both.

== and ~= never cause this error. They work on any two values and simply give false or true.

Causes and fixes

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

• One side was never set (nil)
• Text was compared with a number
• A value object was compared instead of its number

One side was never set (nil)

A value from a table, an attribute or a function that returned nothing is nil. A shop check like if coins >= price then fails for a player whose data has not loaded, or for an item with no price.

local prices = { Sword = 100 }

local function canBuy(coins, item)
	-- "Bow" has no price: attempt to compare nil <= number
	return coins >= prices[item]
end

print(canBuy(150, "Bow"))

Check that both values exist before comparing, and decide what a missing one means.

local prices: { [string]: number } = { Sword = 100 }

local function canBuy(coins: number, item: string): boolean
	local price = prices[item]
	if price == nil then
		warn(`[Shop] no price for {item}`)
		return false
	end
	return coins >= price
end

print(canBuy(150, "Bow"))

Text was compared with a number

A TextBox, an attribute or a string from a data store holds text. Unlike maths, comparisons never convert text, so "50" < 100 fails with string < number even though the text looks like a number.

local box = script.Parent

box.FocusLost:Connect(function()
	-- attempt to compare string < number
	if box.Text < 100 then
		print("small bet")
	end
end)

Convert with tonumber, and handle the case where it is not a number.

local box = script.Parent :: TextBox

box.FocusLost:Connect(function()
	local bet = tonumber(box.Text)
	if bet and bet < 100 then
		print("small bet")
	end
end)

A value object was compared instead of its number

leaderstats.Coins is an IntValue, not a number. Coins >= 50 compares an object with a number and fails with Instance in the message.

local Players = game:GetService("Players")

Players.PlayerAdded:Connect(function(player)
	local coins = player:WaitForChild("leaderstats"):WaitForChild("Coins")
	-- attempt to compare number <= Instance
	if coins >= 50 then
		print("rich")
	end
end)

Compare .Value.

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") and coins.Value >= 50 then
		print("rich")
	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: operators. relational operators
• Roblox Creator Docs: tonumber
• 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, including the swapped order for > and >=, 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.