Packets carry data between your game client and the server. In heavily modded setups, large NBT tags and custom item data can quickly exceed standard network limits. When that happens, the game throws an error and disconnects the player.
Packet Fixer is a Java mod created by TonimatasDEV. It increases packet size limits to stop network data errors from dropping your connection. This adjustment helps modpack creators add more mods without hitting default protocol walls.
Errors it targets
The mod stops specific buffer and allocation failures during network transmission.
You might see messages about NBT tags being too big when syncing complex data, specifically when allocation exceeds 2097152 bytes. So it also handles compressed packets that exceed the 2097152 protocol maximum.
Other prevented errors include attempts to send packets over the 8388608 protocol size limit, along with chunk packets trying to allocate too much memory on read. It stops crashes where packets are larger than 8388608 bytes, payload errors exceeding 1048576 or 32767 bytes, and packet sizes over 8.
It resolves length wider than 21-bit, inability to fit values into 3, connection timeouts, oversized VarLong data, and oversized VarInt data.
If you run into issues with recipes or tags, the author suggests Recipe Fixer instead.
Modpack usage
Large modpacks often generate heavy data payloads. Adding many mods increases the chance that network buffers overflow during regular play.
Packet Fixer is designed for creators to include in their modpacks. It gives your setup extra room by expanding allowed packet thresholds. So that keeps players connected when syncing heavy data.
Compatibility details
Packet Fixer works on Fabric, Neoforge, and Quilt mod loaders.
Supported Minecraft versions are 26.3, 26.2, 1.21.11, 1.21.10, and 1.21.9.
The project record lists client and server sides as optional in its metadata, but the project description states that the mod is required on both client and server sides. Honestly, installing it on both ends ensures network size limits match.
The project is released under the MIT License.
