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 |
