KAllFix
by n1luik
KAllFix is an optimization mod for Forge and NeoForge that uses multithreading, with two main parts controlled mainly through JVM startup parameters.
What it does
The project contains two main parts: KAllFix, a multithreading layer whose features are mostly set by JVM parameters, and a regular config file for the remaining options. Configuration is therefore done largely at launch, so changing a setting means restarting the game with different startup arguments.
Optimizations cover several places in the game. Trims is upgraded to run faster, the Atmospheric mod's date check for April Fools is trimmed so it costs less, and Core receives its own performance upgrade. Client-side use from version 1.0.4.0 on needs the JVM parameter -DKMT Client=true. Some mod combinations still require the mod on the client even when it has no visible effect.
The mod is open source under the GNU General Public License v2.0 only and is published for Forge and NeoForge across 1.19.2 – 1.21.1. Files exist for 1.19.2, 1.20.1, 1.21 and 1.21.1. The latest Forge and NeoForge builds are 1.1.0.6, both marked alpha, with the 1.20.1 Forge build and the 1.21.1 NeoForge build released on 2026-09-13. Source code, an issue tracker and a wiki are linked from the project.
Key features
Multithreaded optimization
The KAllFix layer runs work across threads to reduce the load on the main game thread.
JVM parameter control
Most features are switched on or tuned through JVM startup parameters rather than in-game menus.
Regular config file
A standard config file covers the settings that are not handled through startup parameters.
Trims and Core upgrades
Optimizations are applied to Trims and Core, along with a reduced check for the Atmospheric April Fools date.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Modded packs with lag
Players running large modpacks can use the mod to lighten the work the game does during play, provided the setup works with their other mods.
Client-side tuning
Players who want multithreading on their own client add the -DKMT Client=true JVM parameter from version 1.0.4.0 on.
Who it’s for: Server owners and players who manage JVM startup arguments and want a performance-focused mod for Forge and NeoForge. Because the mod is alpha, server owners should test it before relying on it.
Questions
Does KAllFix have to be installed on both sides?
Which loaders and versions does KAllFix support?
Where should a problem with KAllFix be reported?
In the catalog
KAllFix is one of 3,545 Optimization mods on ModsFinder, and one of 1,441 Optimization mods for Forge. 32,366 mods support Minecraft 1.21.1.
Similar mods
Official listing
- Modrinth page
- modrinth.com/mod/kallfix
- Owner
- n1luik
- Published
- 2025-05-08
- Updated on Modrinth
- 2026-09-13
- Facts verified
- 2026-10-15