PolyMC

PolyMC is a free, open-source launcher for modded Minecraft. It was made because the PolyMC Community felt that the maintainer of MultiMC was not acting in the spirit of Free Software. It is a fork of MultiMC and not endorsed by MultiMC.

Features
Being a fork of MultiMC, PolyMC includes most if not all features of MultiMC, as well as some of its own. Features of PolyMC:
 * Simultaneous control of multiple Minecraft instances.
 * Custom icons and groups for instances.
 * Management of multiple Minecraft user profiles.
 * Ability to play offline.
 * Starting Minecraft with a custom resolution and Java arguments.
 * Changing Java's runtime options (including memory options such as MaxM and MinM).
 * Showing Minecraft's console output in a color coded window.
 * Killing Minecraft easily if it crashes or freezes.
 * Forge integration (automatic installation, version downloads, mod management).
 * Fabric integration (automatic installation, version downloads, mod management).
 * Minecraft world management, with copying and renaming features.
 * Importing and exporting Minecraft instances to share them with anyone.
 * Support for every version of Minecraft that the vanilla launcher does, including snapshots.
 * Management of server and client text logs and in-game screenshots taken during gameplay.
 * Download mods and modpacks directly from within the launcher. The platforms currently supported are Curseforge, Modrinth, Technic, FTB and ATLauncher.