In my experience web workers aren't noticeably slower than regular JS (apart from the cost of copying any shared memory back and forth). They're slower in this

In my experience web workers aren't noticeably slower than regular JS (apart from the cost of copying any shared memory back and forth). They're slower in this demo (for some people but not others), but microbenchmarks in JS are very hard to to do right, and I don't think the author here was trying to make an accurate ubenchmark.