WebKit, an open source Web browser engine used by Safari, App Store, and many other OS X, iOS, and Linux applications, now has a full WebAssembly (wasm) implementation. This is the second major announcement involving wasm in the span of about a week. Just last week, Google announced the company is ending support for Portable Native Client (PNaCl) in favor of wasm.
Now that WebKit has a full WebAssembly implementation, the Safari browser should soon include support for wasm as well (Safari preview version already supports the format). Chrome and Firefox browsers have full support for wasm.
There is a W3C community group that includes representatives from all major browser companies currently working on designing wasm as an open standard.