When It Makes Sense To “Block” The Main Thread

We’ve all heard of the sacred rule in modern web development, the rule never to be broken. The rule of “Never block the main thread.”
You almost can’t miss it as a web developer; it’s in almost every performance guide, and to be fair, it is good advice. We all know the browser’s main thread is single-threaded, meaning it can only do one thing at a time.
Plus, as we know, the main thread isn’t ours alone; we share it with the browser’s rendering eng