based on Eaglercraft 1.8.8 or 1.12.2. They use resource packs and plugins to mimic newer versions but are not native 1.21 builds TuffClient : This is a popular client that supports 1.21 item textures
: New community-driven builds, such as those by independent developers on eaglercraft 1.21 1
Before we focus on version 1.21.1 specifically, it’s important to understand the engine. Eaglercraft is not an "official" Mojang product. Rather, it is a remarkable piece of reverse engineering. Developer "Lax1dude" (and subsequent contributors) took the Java edition of Minecraft and re-compiled it into using a toolchain called TeaVM. based on Eaglercraft 1