Good catch. From my experience though there is a small overhead in terms of workers, also the message cost. But still even if it was 300% slower it's justified

Good catch. From my experience though there is a small overhead in terms of workers, also the message cost. But still even if it was 300% slower it's justified because it is unacceptable to lock the browser. Too many commenters here are coming from the backend, or desktop software where they already have a UI thread. I ask these commenters a simple question, when is the last time you saw your browser freeze? If that doesn't happen often then the devs are doing many things like this to keep that experience enjoyable. Web is it own kind of beast in terms of development, the biggest concern is perceived responsiveness. We get to write off async delays when using webworkers (and similar methods) because users are already used to network requests taking time.