Implements the WebAssembly Core Specification 1.0 Implements several extensions: Threads and atomics Bulk memory operations Conditional data segment initialization Sign-extension operators Non-trapping float-to-int conversions Passes 99.9% of the WebAssembly core semantics test suite Written in C89 and generates C89 Support for many operating systems (e.g. Mac OS X, Mac OS 9, Haiku, Rhapsody, OPEN