Looks like the OP's linked example does not use this, since the sort reported that it took longer when using web workers than when it didn't use web workers, at least a full second longer.

I wonder how much performance would improve if the example did use Transferable Objects.

Note that IE can have some issues with transferable objects.

Also note that the messages cannot encapsulate, say, closures or anything else that you can't JSON.stringify()/JSON.parse().

If one wants to share data with two different web-workers (doing different computations on the same immutable data), there is still a problem. Or so I suppose (?)

Yeah, you'd have to clone the data.

I didn't know this, awesome.