When learning Roblox scripting, one of the most important concepts to understand is the difference between the client and the server.

If you do not understand how they work, you will eventually run into problems like:

• Exploits
• Broken multiplayer systems
• Data not syncing
• UI issues
• Security vulnerabilities

This guide explains the basics in a simple way.

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What is the Server?

The server is the main authority of the game.

It manages:

• Player data
• Game rules
• Damage systems
• Economy systems
• Saving/loading
• NPCs
• Matchmaking

Every player in the game connects to the same server.

The server can see everything happening in the game.

Server Script Location

Server scripts usually run inside:

• ServerScriptService
• Workspace
• ServerStorage

These use normal Script objects.

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What is the Client?

The client is the individual player’s game.

Each player has their own client running on their computer or device.

The client mainly handles:

• UI
• Camera
• Visual effects
• Player input
• Local animations

Clients cannot be trusted because players can modify them using exploits.

Client Script Location

Client scripts use LocalScript.

They usually run inside:

• StarterPlayerScripts
• StarterCharacterScripts
• StarterGui
• Tools

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Client Responsibilities

The client should:

• Detect mouse clicks
• Play swing animations
• Show effects

Server Responsibilities

The server should:

• Detect valid hits
• Deal damage
• Update health
• Prevent cheating

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Why Security Matters

A common beginner mistake is trusting the client too much.

For example:

player.leaderstats.Coins.Value += 100000

If this runs on the client, exploiters could give themselves unlimited coins.

Instead, the server should verify everything.

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Understanding Replication

Replication means data syncing between the server and clients.

Server → Client

Changes made on the server usually replicate to all players.

Example:

part.Color = Color3.new(1, 0, 0)

All players will see the color change.

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Client → Server

Client changes usually do NOT replicate to everyone.

Example:

part.Color = Color3.new(0, 1, 0)

Only that player may see the change.

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RemoteEvents

Since clients and servers are separate, they communicate using RemoteEvents.

Client to Server

Example:

RemoteEvent:FireServer()

Used for:

• Attacking
• Buying items
• Interacting with objects

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Server to Client

Example:

RemoteEvent:FireClient(player)

Used for:

• Notifications
• UI updates
• Effects

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Example Setup

LocalScript

local remote = game.ReplicatedStorage.Attack

script.Parent.MouseButton1Click:Connect(function()
    remote:FireServer()
end)

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Server Script

local remote = game.ReplicatedStorage.Attack

remote.OnServerEvent:Connect(function(player)
    print(player.Name .. " attacked")
end)

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Never Trust the Client

This is one of the biggest rules in Roblox development.

Clients should NEVER decide:

• Damage dealt
• Currency rewards
• Admin permissions
• Item ownership

Always validate important actions on the server.

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Best Practice Split

A good rule is:

Client	Server
UI	Data saving
Input	Damage
Effects	Economy
Camera	Validation
Animations	Security

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Common Beginner Mistakes

1. Saving Data on the Client

Wrong:

LocalScript saving coins

Correct:

Server handles DataStore saving

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2. Damage on the Client

Wrong:

enemy.Humanoid.Health = 0

Exploiters can abuse this.

Damage should always be verified on the server.

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3. Putting Everything in LocalScripts

Many beginners overuse LocalScripts.

Remember:

• LocalScripts are for local player behavior
• Scripts are for game logic

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When to Use LocalScripts

Use LocalScripts for:

• GUI systems
• Camera movement
• Keybind detection
• Visual-only effects
• Smooth responsiveness

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When to Use Server Scripts

Use Scripts for:

• Datastores
• Combat
• Admin systems
• Inventory validation
• Trading systems
• Round systems

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Final Thoughts

Understanding the difference between the client and server is one of the biggest steps toward becoming a better Roblox developer.

If you build your systems correctly from the beginning:

• Your game becomes harder to exploit
• Multiplayer works better
• Scripts become easier to manage
• Performance improves

Most advanced Roblox systems are built around strong client-server architecture.

Learn this early, and future scripting becomes much easier.