HorizonSync
ModA server side mod that allows synchronising player data across different Fabric servers.
Type
Mod
Modrinth Downloads
7
Modrinth ID
XqN44qax
Last Updated
May 16, 2026
Description
HorizonSync
HorizonSync is a high-performance Fabric 1.21.1 mod designed to keep player data synchronized and secure using MongoDB. Whether you are running a single server looking for data redundancy or a network where player progress must be universal, HorizonSync ensures a seamless experience.
Features
Inventory & Equipment Sync: Full synchronization of the main inventory, armor, offhand items, and Ender Chest.
Experience & Stats: Your XP level, bar progress, health, food, and saturation stay exactly as you left them.
Potion Effects: Active status effects are automatically restored when a player joins the server.
High-Performance Persistence: Features a 3-minute asynchronous auto-save system and a synchronous "force-save" on server shutdown to prevent any data loss.
Mod Support
HorizonSync is built with deep integration for the most essential Fabric 1.21.1 APIs and mods:
Accessories API: Full synchronization of accessory slots and cosmetics.
Trinkets API: Complete support for all Trinkets slots.
Sophisticated Backpacks (Unofficial Fabric Port): All backpack contents are serialized and kept in sync.
How It Works
Unlike traditional methods, HorizonSync leverages MongoDB (NoSQL), allowing for extremely fast and flexible data writing:
On Join: Data is retrieved from the cloud and injected into the player via synchronized network packets.
During Gameplay: An asynchronous timer saves changes every 3 minutes without affecting the server's TPS (Ticks Per Second).
On Leave/Shutdown: A final save is performed to ensure every last movement and item is recorded.
Getting Started Installation: Place the HorizonSync .jar file into the mods folder of your Fabric 1.21.1 server.
MongoDB Configuration: Upon the first launch, a config file will be generated in the /config folder. Edit your MongoDB connection string (Local or Atlas) there.
Connection: Ensure your server's IP is whitelisted in your database firewall.
Ready to Go: HorizonSync will automatically create the necessary collections and begin protecting your data.
Configuration Options All settings are managed via the configuration file in the /config directory.
Database Settings uri: Your MongoDB connection string (e.g., mongodb+srv://user:[email protected]/).
database: The name of the database (Default: horizonsync).
collection: The specific collection for player data (Default: playerdata).
FAQ
Q: Why use MongoDB instead of MySQL? A: MongoDB allows for saving complex objects (like Item NBTs) much more efficiently, reducing lag when processing large or modded inventories.
Q: What happens if the server crashes? A: Thanks to the 3-minute auto-save system, data loss is minimized. Players will only lose, at most, their last few minutes of progress.
Q: Is it compatible with Singleplayer? A: HorizonSync is optimized for Dedicated Server environments. It is not recommended for local singleplayer worlds.
Q: Does it support items from other mods? A: Yes. As long as a mod stores its data within the standard Minecraft NBT, HorizonSync will serialize and sync it correctly.
HorizonSync – Your data, always on the horizon, always secure.
Compatibility
Mod Loaders
Game Versions
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