How to Build a Multiplayer Game in Unity in 2025: Complete Beginner Tutorial

Why Unity Wins at Multiplayer in 2025

Let’s be real. You could pick Unreal, Godot, or roll your own engine. But Unity still owns the sweet spot:

• One click, three platforms. PC, iOS, Switch export and done.
• Netcode for GameObjects ships with Unity now. No extra downloads, no weird plugins.
• Asset Store is stacked. Need a lobby UI? Five bucks. Need voice chat? Ten.
• Community size. Stuck at 3 a.m.? There’s a Discord server awake somewhere.

Oh, and Unity Relay (their free matchmaking service) just dropped zero-config lobbies. That alone saved me two days of Googling server stuff.

What You’ll Build Today

Picture this: a tiny 2D arena where up to four players throw paint at each other. Simple. Chaotic. Perfect to learn the ropes.

Here’s the plan:

1. Create the project (5 min)
2. Add Netcode (10 min)
3. Spawn players and sync color (15 min)
4. Test on two machines (5 min)
5. Ship a tiny itch.io build so friends can join (priceless)

Let’s cut to the chase.

Step 1: Create the Project Like a Pro

Open Unity Hub. Use 2022 LTS or newer anything older will fight you on Netcode.

1. Click New Project → 2D (URP)
2. Name it “PaintBrawl2025”
3. Tick “Enable Git” so you don’t lose work when your cat walks on the keyboard

Folder trick: Right-click in Assets and make these folders:

• _Scripts
• _Prefabs
• _Scenes
• _Art

Trust me, future you will thank present you.

Step 2: Install Netcode in 30 Seconds

Window → Package Manager → Unity Registry.
Search “Netcode for GameObjects”. Hit Install. Done.

Pro tip: While it downloads, grab a free pixel-art sprite pack from the Asset Store. We’ll need something to throw.

Step 3: Add the NetworkManager

Create an empty GameObject. Name it NetworkManager.
Add the NetworkManager component.
In the Transport slot, pick UnityTransport.

Think of the NetworkManager as the party host. It decides who can enter, who can talk, and who gets kicked out for eating all the chips.

Step 4: Make a Player Prefab That Actually Syncs

1. Drag your sprite into the scene.
2. Add NetworkObject component.
3. Add NetworkTransform to sync movement.
4. Create a new script PlayerPaint.cs and paste:

using Unity.Netcode;
using UnityEngine;
 
public class PlayerPaint : NetworkBehaviour
{
    public GameObject paintBlobPrefab;
    public float throwForce = 5f;
 
    void Update()
    {
        if (!IsOwner) return; // Only let the owner throw
 
        if (Input.GetMouseButtonDown(0))
        {
            Vector3 mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
            Vector2 direction = (mousePos - transform.position).normalized;
            ThrowServerRpc(direction);
        }
    }
 
    [ServerRpc]
    void ThrowServerRpc(Vector2 dir)
    {
        GameObject blob = Instantiate(paintBlobPrefab, transform.position, Quaternion.identity);
        blob.GetComponent<NetworkObject>().Spawn();
        blob.GetComponent<Rigidbody2D>().velocity = dir * throwForce;
    }
}

Drag the script onto the sprite.
Drag the sprite back to Assets/_Prefabs to make a prefab.
Delete the one in the scene we’ll spawn it later.

Step 5: Spawning Players (No One Gets Left Behind)

Create an empty GameObject. Name it GameManager.
Add script GameManager.cs:

using Unity.Netcode;
using UnityEngine;
 
public class GameManager : NetworkBehaviour
{
    [SerializeField] private GameObject playerPrefab;
 
    public override void OnNetworkSpawn()
    {
        if (IsServer)
        {
            SpawnPlayerServerRpc(NetworkManager.Singleton.LocalClientId);
        }
    }
 
    [ServerRpc(RequireOwnership = false)]
    private void SpawnPlayerServerRpc(ulong clientId)
    {
        GameObject player = Instantiate(playerPrefab);
        player.GetComponent<NetworkObject>().SpawnAsPlayerObject(clientId);
    }
}

Assign the player prefab in the inspector.
Hit Play, then click Host (LAN).
Open a second Unity window with ParrelSync (free Asset Store tool) and click Client. Boom two players moving and throwing.

Feels like magic, right?

Step 6: Add a Splash of Color (Syncing Variables)

We want each player to have a random color. Easy.

Inside PlayerPaint.cs, add:

[SerializeField] private SpriteRenderer bodyRenderer;
private NetworkVariable<Color> netColor = new NetworkVariable<Color>();
 
public override void OnNetworkSpawn()
{
    if (IsServer)
        netColor.Value = Random.ColorHSV(); // Server decides color
    bodyRenderer.color = netColor.Value;
}

Now every player sees the same colors. No more “why am I blue on my screen but red on yours?”

Step 7: Test on Real Devices (Because Wi-Fi Lies)

1. Build & Run → PC, Mac & Linux Standalone.
2. Check Server Build.
3. Run the build, click Host.
4. In Unity Editor, Play → Client and type the local IP (192.168.x.x).
5. Throw some paint. Notice any lag? If yes, lower the Send Rate in UnityTransport from 60 to 30.

Step 8: Ship It on itch.io in 5 Minutes

1. Build again, this time uncheck Server Build.
2. Zip the folder.
3. Create itch.io account → Upload → Set price to “free or donation”.
4. In the Networking section of itch, add a note: “Click Host if you’re first, else click Join and enter host’s IP.”

Invite your group chat. Watch chaos ensue.

Common Gotchas (and How to Dodge Them)

• Physics out of sync?
  Make sure Rigidbody2D is on the prefab and NetworkTransform syncs velocity.

• Player spawns on top of each other?
  Add random spawn points in GameManager.cs:

Vector3 spawnPos = new Vector3(Random.Range(-5, 5), Random.Range(-3, 3));
player.transform.position = spawnPos;

• Firewalls block connections?
  Windows Defender hates indie devs. Add an outbound rule for your game exe.

Next Steps: From Prototype to Steam

• Add Unity Relay so no IP sharing. Free tier handles 100 CCU.
• Steamworks SDK for lobbies, friends list, achievements. Takes about a day.
• Voice chat with Vivox also free under 5k monthly users.
• Analytics with Unity Gaming Services to spot rage-quit moments.

Quick FAQ

Do I need a dedicated server?
Nope. Start with Host/Client model. Scale later if you hit 100+ players.

Can I do this in 3D?
Same steps. Swap sprites for cubes. Unity doesn’t care.

Is Netcode stable?
Been production-ready since 2023. Ubisoft uses it for mobile titles. You’re safe.

“If you can make one person laugh, you can make millions play together.” Some indie dev on Twitter

Ready to paint the town red (and blue, and green)? Go build.

#UnityMultiplayer #GameDev2025 #IndieDevTips