Using XXL Packets with Large Datapacks and Recipe-Heavy Modpacks

The Recipe Sync Problem

Servers with many recipes — from large datapacks, extensive modpacks, or custom crafting additions — send a recipe synchronization packet when a player joins. In vanilla, this packet has a hard size cap. Once your recipe count grows past what fits, every joining client gets kicked. This is a known vanilla bug that this mod addresses by raising the cap.

Practical Setup

1. Install the mod on the server and on every client.

2. If you run a distributed modpack, bundle the mod into the pack so clients receive it automatically.

3. Restart both server and clients after installation.

4. Join with a modded client and verify the recipe sync completes without a disconnect.

Scaling Your Datapack

Once the mod is in place, you can expand your datapacks and recipe sets without worrying about the join-time packet limit. Keep in mind the raised limit is very large but not infinite — extremely bloated data can still cause issues, and performance may suffer from sheer volume regardless of packet size.

Multiplayer Considerations

Every connecting player needs the mod. If you run a public server, document this requirement prominently. Players without it will be unable to join recipe-heavy worlds, and the error they see may not clearly explain why.