[izym]

I can't remember if threading support is in yet, but it should be possible. The downside is that it will be a rather hefty binary the user has to download.

[markdog12]

No threads yet, they're coming though: http://webassembly.org/docs/future-features/

[douche]

Eh, cut one tracking script or bloated PNG and you've saved a lot of download size.