Didn't read it through yet, but someone gave me the link to #heading-what-are-microtasks and the first affirmation in this paragraph is not correct, you can queue microtasks yourself with the queueMicrotask method, and specs can queue microtasks as they will, for instance HTML does queue a microtask to update the image data of <img>, so that you can set the .crossOrigin or loading attributes after the src one, in the same task, without triggering useless network requests.