Eaglercraft is an open-source implementation of Minecraft that runs entirely in a web browser using JavaScript and WebAssembly (WASM), requiring no server-side plugins or client installations. This paper analyzes the architecture, performance characteristics, and technical constraints of Eaglercraft’s WASM-based runtime. We explore how the game compiles Java-based Minecraft logic to WASM, manages rendering via WebGL, and achieves real-time networking through WebSockets. Benchmarks show that while WASM introduces some overhead compared to native Java, it delivers consistent 30–60 FPS on modern browsers, making it a viable solution for sandboxed, cross-platform Minecraft gameplay.