Mastering GetDescendants() in Roblox Lua: A Complete Guide

When you start scripting in Roblox, one of the most powerful skills you can learn is how to navigate and control the hierarchy of objects in a game. Every game you build is made of Instances (parts, models, GUIs, sounds, scripts, etc.), and these Instances are arranged in a tree-like structure. Sometimes, you need to grab a specific object. Other times, you want everything inside of something — and that’s where GetDescendants() shines.

This article will guide you through what GetDescendants() is, how it works, when to use it, common mistakes, performance tips, and advanced tricks. By the end, you’ll know exactly how to wield it like a pro.

What Is GetDescendants()?

In Roblox, almost every object is an Instance. Each Instance can have children (objects directly inside of it). You may already know about GetChildren(), which returns the direct children of an Instance.

But what if you want every object inside, no matter how deeply nested? That’s where GetDescendants() comes in.

👉 Definition:Instance:GetDescendants() returns an array (table) containing all descendants of the Instance — that means children, children of children, children of children of children, and so on.

Example: The Difference Between GetChildren() and GetDescendants()

Let’s say you have this structure:

• Model:GetChildren() → returns {Part, Folder}

• Model:GetDescendants() → returns {Part, Folder, Part}

Notice how GetDescendants() digs deeper and grabs everything inside.

Basic Usage

Here’s a simple script that prints all descendants of Workspace:

for _, descendant in pairs(workspace:GetDescendants()) do
    print(descendant.Name)
end

This will list the name of every single object in your Workspace, no matter how nested.

Filtering Descendants

Of course, you don’t always want all objects. You might just want all the Parts in a Model.

local model = workspace.MyModel

for _, descendant in pairs(model:GetDescendants()) do
    if descendant:IsA("Part") then
        print("Found part: " .. descendant.Name)
    end
end

👉 Here we’re using .IsA() to filter out only objects of type Part. This is super common when you want to change properties like color, material, or collision.

Practical Example 1: Changing All Parts in a Model

Let’s say you’ve built a house in Studio and grouped it into a Model called House. You want to turn every part in the house red:

local house = workspace.House

for _, descendant in pairs(house:GetDescendants()) do
    if descendant:IsA("BasePart") then
        descendant.Color = Color3.fromRGB(255, 0, 0)
    end
end

Now every wall, roof piece, and floor tile becomes red — even if they were hidden inside folders or nested models.

Practical Example 2: Adding ClickDetectors Everywhere

Suppose you want to make every part in a Model clickable. Instead of manually inserting a ClickDetector into each Part, you can script it:

local model = workspace.House

for _, descendant in pairs(model:GetDescendants()) do
    if descendant:IsA("BasePart") then
        local detector = Instance.new("ClickDetector")
        detector.Parent = descendant
    end
end

This is where GetDescendants() saves you hours of manual work.

When Should You Use GetDescendants()?

✅ Great Use Cases

• Bulk editing properties across many objects

• Adding or removing items (like ClickDetectors, TouchTransmitters, or SurfaceGuis)

• Searching deeply nested structures for specific objects

• Applying scripts to procedurally generated models

⚠️ When to Be Careful

• Large Hierarchies: If you call GetDescendants() on something huge (like Workspace in a large game), it can return thousands of objects.

• Performance: Don’t spam it in RunService.Heartbeat or loops that run constantly. Use it when you need a snapshot, not repeatedly.

Performance Tips

1. Don’t Overuse It – If you only need direct children, use GetChildren(). It’s faster.

2. Cache Results – If your hierarchy won’t change often, call GetDescendants() once and reuse the results instead of calling it repeatedly.

3. Filter Early – Check IsA() before running heavy logic to avoid unnecessary work.

   
   

Advanced Trick 1: Combining with CollectionService

Sometimes, instead of scanning through everything, you can “tag” objects using CollectionService in Studio. But if you’ve already got a model and you want to quickly find all tagged descendants:

This combines the power of tags with deep searching.

Advanced Trick 2: Recursive Behavior Without GetDescendants()

For learning purposes, here’s how you could manually write your own GetDescendants() using recursion:

local function getAllDescendants(object)
    local descendants = {}
    for _, child in pairs(object:GetChildren()) do
        table.insert(descendants, child)
        for _, grandChild in pairs(getAllDescendants(child)) do
            table.insert(descendants, grandChild)
        end
    end
    return descendants
end

-- Example:
local myModel = workspace.House
local allDescendants = getAllDescendants(myModel)
print(#allDescendants)

This helps you understand what’s happening under the hood — GetDescendants() is basically a built-in recursive function.

Common Mistakes to Avoid

1. Using It in Loops Every Frame

   game:GetService("RunService").Heartbeat:Connect(function() for _, d in pairs(workspace:GetDescendants()) do -- laggy! end end)

   ❌ This will destroy performance in big games.

2. Not FilteringIf you don’t check IsA(), you might try changing .Color on an object that doesn’t have that property, causing errors.

3. Confusing It with GetChildren()Beginners often mix these up. Remember:

   • GetChildren() = direct children only

   • GetDescendants() = everything inside

   
   

Real-World Example: Lighting System

Let’s say you’re building a dungeon and want every torch (a Part with a PointLight inside) to turn off at once.

local dungeon = workspace.Dungeon

for _, descendant in pairs(dungeon:GetDescendants()) do
    if descendant:IsA("PointLight") then
        descendant.Enabled = false
    end
end

With one loop, every torchlight in your dungeon is turned off — no matter how deep inside the models they are.

Wrapping It All Up | Roblox GetDescendants

GetDescendants() is one of those functions that feels small but unlocks huge possibilities in Roblox scripting. It lets you:

• Traverse complex hierarchies

• Apply bulk changes to objects

• Save time compared to manually editing every part

• Create scalable, reusable systems

But like all powerful tools, you have to use it wisely. Don’t overuse it in performance-heavy situations. When you need speed, stick to GetChildren() or tagging systems.

Think of GetDescendants() as your treasure map through Roblox’s Instance hierarchy. With it, you can uncover and control every hidden piece of your game world.