Because Eaglercraft uses Minecraft's original code, it exists in a legal gray area. Always download from reputable GitHub contributors to avoid malware bundled as "offline clients."

: Original source code and verified offline HTML files are preserved in repositories like neon443/eaglercraft-1.5.2-Original and the Eaglercraft-Archive. Technical Architecture

How to Download & Play Eaglercraft 1.5.2 Offline (No Internet Required)

Even though it’s offline, the game still uses browser resources. Close extra tabs to give Eaglercraft more RAM.