Tracking the mouse

Tracking user’s eye movements is essentially impossible without special equipment and testing, but if you can capture their mouse and show that it matches their eyes pretty closely, you have some rather solid data.

If you want to know exactly how people are using your website, you can run focus groups and do other testing to get a very good look at it. However, for a fraction of the price and effort you can use tools like heatmaps and be confident that the results are 80%+ the same as if you were able to track their eyes.