How fast are Selenium Webdriver "Actions" performed?

I've been playing around with Selenium (chromedriver, Java). I got interested in seeing what it would take to make Selenium move the mouse around in a human-like way; this led me to the Selenium Actions class.

How fast are Selenium Actions performed? I figure this is important to know if I want to move the mouse with a specific velocity. I tried executing the following code:

    Actions builder = new Actions(driver);
    Action action = builder.moveByOffset(4,0).build();
    LocalTime before =;
    for (int i = 0; i < 100; i++) {
    LocalTime after =;
    System.out.println(Duration.between(before, after).toMillis());

If I run this code on "about:blank" or a plain html page stored on my local system, this runs in ~1700ms. If I run this a website like, it runs in ~300ms. Can someone explain to me what's going on?