What is !strict

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1

what is !strict i saw it in scripts but idk what it does

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Hope that helped.

Specifically: Type checking | Documentation - Roblox Creator Hub

It’s just a type checking mode that determines how the roblox debugger will handle your scripts.

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strict allows for strict typing
like giving warnings when a wrong type is used

(There are strictly types languages and dynamically types languages Luau is dynamically typed
but using --!strict allows for strict typing in luau)

example

--!strict
local str = "Hello World!"

str = 5 -- error type number cannot be converted into string

--!strict
local str : string | number = "Hello World!"

str = 5 -- no error

you can find a lot of tutorials about it by searching

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pretty much what the others said. It highlights typechecking issues. It can be helpful for pointing out small issues in code logic, too.

Pointing out small typos 
--!strict

local label = script:WaitForChild("TextLabel") :: TextLabel
local var = script:GetAttribute("SomeAttribute_CFrame") :: CFrame

--imagine you had some text here you retrieved from somewhere else
local text = "blah blah"

--you accidentally wrote var instead of text...
label.Text = var -- Value of type 'CFrame' could not be converted into type 'string'
Typechecking 
local foo = 3
print(string.find(
    foo, --type 'number' could not be converted into 'string'
    "hi"
))

local function foo(a: number, b: number)
    --...
end

foo(3) --function 'foo' expects 2 arguments but only 1 was specified

local function bar(a: number, b: number?)
    --...
end

bar(3) --no warning

there’s a bunch more examples but here’s a few

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