Experimental features

info

Experiments are only available in Legacy Launcher 160.0 or newer

What is it?

Experiments are potentially unstable features that we are not ready to enable for all users by default

How to enable?

1. Close Legacy Launcher
2. Open the Legacy Launcher configuration file with any text editor (e.g. Notepad++).
   Where can I find the Legacy Launcher configuration file?

   Most often it will be located either in the .tlauncher/legacy.properties folder, or in the tl.properties file in the launcher install (e.g. .tlauncher/legacy/Minecraft/tl.properties)

3. Find the experiments.available line in the opened file - this is the list of available experiments
4. Find the experiments.enabled line in the opened file and write there the list of required experiments via ;
   legacy.properties

   # Available experiments list
   experiments.available=zgc;zgc_generational;shenandoah;tenuring;max_xms;updated_lwjgl;updated_jna
   # "none" will disable all experiments
   experiments.enabled=none
   # Example to enable "updated_lwjgl" and "updated_jna" experiments
   experiments.enabled=updated_lwjgl;updated_jna
5. Start Legacy Launcher

Experiments list

note

zgc, zgc_generational, shenandoah, tenuring and max_xms experiments require "optimized arguments" feature

warning

zgc and shenandoah experiments were moved to the updated "Optimized arguments" option and no more considered experimental

• zgc - replaces CMS/G1 in the "optimized arguments" with ZGC. This garbage collector is quite efficient, but requires a very powerful CPU. ZGC was automatically enabled in older versions of LL on powerful PCs. Requires Java 15 or newer.
• zgc_generational - enables "generations" support in ZGC, which should improve its performance. Requires Java 21 or newer and a zgc experiment.
• shenandoah - replaces CMS/G1/ZGC in "optimized arguments" with Shenandoah. This garbage collector should be best suited for Minecraft, as it claims to provide the shortest possible RAM cleanup time. Requires Java 11 or newer.
• tenuring - Changes the MaxTenuringThreshold parameter of the garbage collector so that quickly aging data in game memory is "aged" slower and cleared faster. Should reduce the stutters duration during memory cleanup. When using G1, these parameters are applied by default, the experiment enables this feature for other garbage collectors.
• max_xms - allocates the entire selected RAM amount at the game startup.
• updated_lwjgl - Forcibly updates LWJGL on versions using LWJGL3 to 3.3.2. Recommended for solving Apple Silicon (M1/M2/M3/...) issues.
• updated_jna - Forcibly updates JNA on versions that use it to 5.13.0. Recommended for solving macOS issues.