Depends on loads of different factors. How deep are you squatting? What position are your feet in? Are you using a hip hinge movement (ie. folding at hips first, which is healthy) or leaning/hunching forward to get your body closer to the ground? Do your heels come up when you're at the bottom of the squat? Are you using weights with your squats, or just bodyweight? How's your flexibility in hip flexors/ankle dorsiflexion/knees/lower back in general?
Try doing a few squats in front of a mirror, and watch your alignment from the side as you squat - then compare your movement to the videos/diagrams you're using. Do they match? Pay close attention to your hip movement and knee placement (like
CherryPie mentions) as well as how low your bum gets - the top of your leg should ideally be parallel to the floor.
If you're not hitting those cues, keep watching yourself in the mirror and go slowly to make sure you're being mindful of what position your body is in. You're almost always much better off to do 5 squats with good form than 30 quasi-squats.
And have fun!