Answer : WebAssembly vs asm.js First, let's take a look how, in principle, WebAssembly is different from asm.js , and whether there's potential to reuse existing knowledge and tooling. The following gives pretty good overview: Why create a new standard when there is already asm.js? What is the difference between asm.js and web assembly? Why WebAssembly is Faster Than asm.js Let's recapitulate, WebAssembly (MVP, as there's more on its roadmap, roughly): is a binary format of AST with static typing, which can be executed by existing JavaScript engines (and thus JIT-able or compiled AOT), it's 10-20% more compact (gzipped comparison) and an order of magnitude faster to parse than JavaScript, it can express more low-level operation that won't fit into JavaScript syntax, read asm.js (e.g. 64-bit integers, special CPU instructions, SIMD, etc) is convertible (to some extent) to/from asm.js. Thus, currently WebAssembly is an iteration on asm.js and targets only C/C+