How to i fit a GUI on everyone's screen at the same position?

repeat wait() until workspace.CurrentCamera.ViewportSize ~= Vector2.new()
function toScale(instance)
for _,v in pairs(instance:GetChildren()) do
if v:IsA("GuiObject") then
local size = v.Parent:IsA("GuiObject") and v.Parent.AbsoluteSize or workspace.CurrentCamera.ViewportSize
local pos = v.AbsolutePosition - (v.Parent:IsA("GuiObject") and v.Parent.AbsolutePosition or Vector2.new())
v.Size = UDim2.new(v.AbsoluteSize.X/size.X, 0 , v.AbsoluteSize.Y/size.Y)
v.Position = UDim2.new(pos.X/size.X, 0 , pos.Y/size.Y)
end
toScale(v)
end
return
end
toScale(game.StarterGui)
20,000,000

Instead of using Offset, use scale!

If you look at the Position of a Gui, it probably looks something like this:

{0, 200},{0, 500}  -- Attempted middle of the screen

The solution then is to use the Scale (the 0's in the first example)

{0.5, 0},{0.5, 0} -- The middle of the screen

One thing you should note though, is the above solution sets the top left of the Gui Element in the middle of the screen. If you want a Gui to be centered, you will need to use the following:

-- Position = {0.5, 0},{0.5, 0} This is the middle of the screen. 
-- Using this will make the top left of a Gui in the middle of the screen

To center a Gui, we will use the following

Position = {.5, -Gui_Element.Size.X.Offset / 2, .5, -Gui_Element.Size.Y.Offset / 2}

Note that you do not need to script this. In fact, I don't recommend scripting it. In Studio, in the Properties box, follow the same format and do the math yourself by diving the x and y values of Size by 2 and then making them negative.