Roblox GUI Reference

GUI Container Types

Container	Parent	Use Case
ScreenGui	PlayerGui	HUDs, menus, overlays — always faces screen
SurfaceGui	BasePart	World-space UI on a part surface (signs, screens)
BillboardGui	BasePart or Model	Floats above a part in 3D space (name tags, health bars)

ScreenGui

-- LocalScript in StarterGui or StarterPlayerScripts
local player = game:GetService("Players").LocalPlayer
local playerGui = player:WaitForChild("PlayerGui")

local screenGui = Instance.new("ScreenGui")
screenGui.Name = "HUD"
screenGui.ResetOnSpawn = false   -- keep GUI across respawns
screenGui.ZIndexBehavior = Enum.ZIndexBehavior.Sibling
screenGui.Parent = playerGui

SurfaceGui

local surfaceGui = Instance.new("SurfaceGui")
surfaceGui.Face = Enum.NormalId.Front
surfaceGui.SizingMode = Enum.SurfaceGuiSizingMode.PixelsPerStud
surfaceGui.PixelsPerStud = 50
surfaceGui.Parent = workspace.ScreenPart

local label = Instance.new("TextLabel")
label.Size = UDim2.fromScale(1, 1)
label.Text = "Hello World"
label.Parent = surfaceGui

BillboardGui

local billboard = Instance.new("BillboardGui")
billboard.Size = UDim2.fromOffset(200, 50)
billboard.StudsOffset = Vector3.new(0, 2.5, 0)  -- float above head
billboard.AlwaysOnTop = false
billboard.Parent = character:WaitForChild("Head")

local nameLabel = Instance.new("TextLabel")
nameLabel.Size = UDim2.fromScale(1, 1)
nameLabel.BackgroundTransparency = 1
nameLabel.Text = player.DisplayName
nameLabel.Parent = billboard

---

UDim2 Sizing and Positioning

UDim2.new(xScale, xOffset, yScale, yOffset) — scale is 0–1 relative to parent, offset is pixels.

frame.Size     = UDim2.new(1, 0, 0, 50)       -- full width, 50px tall
frame.Position = UDim2.new(0, 0, 0, 0)         -- top-left corner

frame.Size     = UDim2.fromScale(0.6, 0.4)     -- 60% wide, 40% tall
frame.Position = UDim2.new(0.2, 0, 0.3, 0)    -- centered (0.2 = (1-0.6)/2)

UDim2.fromScale(0.5, 0.5)    -- scale only
UDim2.fromOffset(300, 150)   -- pixels only

AnchorPoint shifts the element's pivot (0–1 on each axis):

frame.AnchorPoint = Vector2.new(0.5, 0.5)   -- pivot at center
frame.Position    = UDim2.fromScale(0.5, 0.5)  -- truly centered on screen

---

Responsive Design

Prefer scale over offset so UI adapts to all screen sizes.

button.Size     = UDim2.fromScale(0.2, 0.07)
button.Position = UDim2.new(0.4, 0, 0.85, 0)

-- Prevent distortion with UIAspectRatioConstraint
local arc = Instance.new("UIAspectRatioConstraint")
arc.AspectRatio = 4   -- width:height = 4:1
arc.Parent = button

---

TweenService Animations

local TweenService = game:GetService("TweenService")
local tweenInfo = TweenInfo.new(0.3, Enum.EasingStyle.Quad, Enum.EasingDirection.Out)

local menuFrame = script.Parent

local function openMenu()
    TweenService:Create(menuFrame, tweenInfo, {
        Position = UDim2.new(0.05, 0, 0.1, 0)
    }):Play()
end

local function closeMenu()
    TweenService:Create(menuFrame, tweenInfo, {
        Position = UDim2.new(-0.5, 0, 0.1, 0)
    }):Play()
end

-- Animated progress bar
local function setProgress(bar, pct)
    TweenService:Create(bar, TweenInfo.new(0.2), {
        Size = UDim2.new(pct, 0, 1, 0)
    }):Play()
end

---

LocalScript Placement

Location	Notes
StarterGui	Cloned into PlayerGui on join; use ResetOnSpawn = false to persist
StarterPlayerScripts	Runs once, not reset on respawn; good for persistent managers
StarterCharacterScripts	Re-runs each spawn; suited for character-dependent UI

-- Safe pattern: wait for character
local player = game:GetService("Players").LocalPlayer
local character = player.Character or player.CharacterAdded:Wait()
local humanoid = character:WaitForChild("Humanoid")

humanoid.HealthChanged:Connect(function(health)
    -- update health bar
end)

---

ResetOnSpawn

screenGui.ResetOnSpawn = false  -- persist across respawns (inventory, settings)
screenGui.ResetOnSpawn = true   -- re-create on respawn (respawn timer) — default

---

Common Patterns Quick Reference

Pattern	Key Setup
Full-screen overlay	Size = UDim2.fromScale(1,1), Position = UDim2.fromScale(0,0)
Bottom-center HUD bar	AnchorPoint = (0.5,1), Position = UDim2.new(0.5,0,1,-10)
Padded list	UIPadding + UIListLayout inside a Frame
Scrollable list	ScrollingFrame + UIListLayout; set CanvasSize from UIListLayout.AbsoluteContentSize
Rounded corners	UICorner with CornerRadius = UDim.new(0, 8)
Scaled text	TextScaled = true on TextLabel/TextButton so font grows with container
Dynamic frame height	AutomaticSize = Enum.AutomaticSize.Y so frame expands to fit children
Health bar	Nested frames: outer = background, inner tweened by Size.X.Scale
Name tag	BillboardGui on Head, StudsOffset = Vector3.new(0, 2.5, 0)

---

Common Mistakes

Mistake	Fix
GUI disappears on respawn	Set ResetOnSpawn = false or use StarterPlayerScripts
UI looks wrong on mobile	Use UDim2.fromScale + UIAspectRatioConstraint
Script can't find PlayerGui	Use player:WaitForChild("PlayerGui")
Tween doesn't run	Ensure the property is tweenable; Text is not, Position and Size are
BillboardGui visible through walls	Verify AlwaysOnTop = false
AbsoluteSize is zero on first frame	Read it inside task.defer or after first render step
Clicks pass through overlapping frames	Add a transparent input-blocking Frame or set Modal = true
SurfaceGui flickers	Set LightInfluence = 0; ensure part isn't too thin
Text tiny on mobile	Set TextScaled = true — fixed TextSize doesn't adapt to screen size
UI hard to test on mobile	Use Studio's Device Emulator (Test tab → Device) to preview layouts