Oh dear sorry about this, it's a little too non-obvious how to see the demo! I've [pushed a small commit](https://github.com/rustwasm/wasm-bindgen/commit/f016ae5846bf...) to update the demo to include information about browser requirements. Today this demo requires Firefox Nightly (64) and requires the `javascript.options.shared_memory` feature to be enabled. Other browsers will likely soon be able to run the demo as well!