Unity Netcode overview

Introduction

Unity Netcode helps you make games where many players can play together over the internet. It makes sharing game data between players easy and smooth.

You want to create a multiplayer game where players can see and interact with each other.

You need to sync player movements and actions in real-time across different devices.

You want to manage game events like scoring or health changes for all players at once.

You want to build a cooperative or competitive game that works online.

You want to handle player connections and disconnections smoothly.

Syntax

Unity

using Unity.Netcode;

public class MyNetworkScript : NetworkBehaviour
{
    public NetworkVariable<int> playerScore = new NetworkVariable<int>(0);

    public override void OnNetworkSpawn()
    {
        if (IsServer)
        {
            playerScore.Value = 10;
        }
    }
}

NetworkBehaviour is a special class for scripts that work with Unity Netcode.

NetworkVariable is used to share data like numbers or positions between players automatically.

Examples

This creates a shared health value starting at 100 that all players can see.

Unity

public NetworkVariable<int> health = new NetworkVariable<int>(100);

Only the server can change the health value to keep data consistent.

Unity

if (IsServer)
{
    health.Value -= 10;
}

Use IsOwner to run code only for the player controlling this object.

Unity

public override void OnNetworkSpawn()
{
    if (IsOwner)
    {
        // This code runs only for the player who owns this object
    }
}

Sample Program

This simple script lets the player press space to increase their score. The score is shared with all players using Unity Netcode. The server updates the score and all players see the change.

Unity

using UnityEngine;
using Unity.Netcode;

public class SimplePlayer : NetworkBehaviour
{
    public NetworkVariable<int> score = new NetworkVariable<int>(0);

    void Update()
    {
        if (!IsOwner) return;

        if (Input.GetKeyDown(KeyCode.Space))
        {
            IncreaseScoreServerRpc();
        }
    }

    [ServerRpc]
    void IncreaseScoreServerRpc()
    {
        score.Value += 1;
        Debug.Log($"Score updated to {score.Value}");
    }

    public override void OnNetworkSpawn()
    {
        score.OnValueChanged += (oldValue, newValue) =>
        {
            Debug.Log($"Score changed from {oldValue} to {newValue}");
        };
    }
}

Important Notes

Always run data changes on the server to keep the game fair and synced.

Use NetworkVariable for simple shared data like scores or health.

Use ServerRpc to send commands from players to the server.

Summary

Unity Netcode helps you build multiplayer games by sharing data between players easily.

Use NetworkBehaviour and NetworkVariable to sync game data.

Server controls data changes to keep the game fair and consistent.