Saving & Loading Games

Save the player's progress to a file and load it back, using a plain C# class and JSON.

PlayerPrefs or a save file?

Step 1: describe what to save

Make a plain class that holds only the data. [System.Serializable] means "this can be turned into text".

using System.Collections.Generic;
using UnityEngine;

[System.Serializable]
public class SaveData
{
    public int coins;
    public int health = 100;
    public string levelName = "Level1";
    public Vector3 playerPosition;
    public List<string> inventory = new List<string>();
}

JsonUtility saves public fields (or [SerializeField] private ones). It can't save properties, Dictionary, or references to GameObjects. Save an ID or name instead, like "sword_01".

Step 2: the save system

using System.IO;
using UnityEngine;

public static class SaveSystem
{
    private static string PathFor(int slot) =>
        Path.Combine(Application.persistentDataPath, $"save{slot}.json");

    public static void Save(SaveData data, int slot = 0)
    {
        string json = JsonUtility.ToJson(data, prettyPrint: true);
        File.WriteAllText(PathFor(slot), json);
    }

    public static SaveData Load(int slot = 0)
    {
        string path = PathFor(slot);
        if (!File.Exists(path)) return new SaveData();   // no save yet: fresh game

        try
        {
            return JsonUtility.FromJson<SaveData>(File.ReadAllText(path));
        }
        catch (System.Exception e)
        {
            Debug.LogWarning($"Save file was broken, starting fresh: {e.Message}");
            return new SaveData();
        }
    }

    public static bool HasSave(int slot = 0) => File.Exists(PathFor(slot));
    public static void Delete(int slot = 0) => File.Delete(PathFor(slot));
}

Step 3: use it

using UnityEngine;

public class GameSaver : MonoBehaviour
{
    [SerializeField] private Transform player;
    [SerializeField] private Wallet wallet;   // your own coin script

    public void SaveGame()
    {
        var data = new SaveData
        {
            coins = wallet.Coins,
            playerPosition = player.position,
        };
        SaveSystem.Save(data);
    }

    public void LoadGame()
    {
        SaveData data = SaveSystem.Load();
        wallet.SetCoins(data.coins);
        player.position = data.playerPosition;
    }
}

Hook SaveGame and LoadGame up to buttons with a UnityEvent, or call SaveGame at checkpoints.

What the file looks like

{
    "coins": 42,
    "health": 100,
    "levelName": "Level1",
    "playerPosition": { "x": 3.5, "y": 1.0, "z": -2.0 },
    "inventory": [ "sword_01", "potion_small" ]
}

To find it, log Application.persistentDataPath. On Windows it's inside AppData\LocalLow\<company>\<product>. It's plain text, so you can read it (and so can players).

Good habits

• Add a version number (public int version = 1;). When you change SaveData later, you can tell old saves apart.
• New fields are safe: loading an old file leaves missing fields at their default values.
• Save IDs, not objects: store "potion_small" and look it up in a list of ScriptableObject items when loading.
• Need dictionaries? Use the Newtonsoft JSON package (com.unity.nuget.newtonsoft-json); see Free Libraries.
• WebGL: file saving works differently in the browser. Test there early if you're publishing to the web.

Common Mistakes

• Saving to Application.dataPath (inside the game folder). In a finished game it often can't be written to, and on some platforms it's read-only. Use persistentDataPath.
• Forgetting [System.Serializable], or using properties, so the file comes out as {}.
• Trying to save a GameObject or Transform directly.
• Not handling "no save file yet" on the very first launch.

See also

• PlayerPrefs
• Exceptions & try/catch
• Building Your Own Systems

This page is a simplified, AI-assisted interpretation. For the complete and authoritative reference, see the official documentation.