HorizonSync
ModA server side mod that allows synchronising player data across different Fabric servers.
Type
Mod
Modrinth Downloads
24
Modrinth ID
XqN44qax
Last Updated
Jun 25, 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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