Question

i know that there are websites which can detect where the mouse is moving on the screen on a website, and then display a movie of that visit. like robotreplay or clicktale.

how do they do that?

Answer 1

Use the onmousemove event handler to capture the mouse move. Than you can read the x and y coordinates of the mouse cursor:

window.onmousemove = function(e) {
    document.documentElement.innerHTML = e.x + ":" + e.y;
};