This standard is meant to protect the mental, emotional and physical well-being of a child, and ensure their parents are fit to provide them with the best possible upbringing. It applies whether the judge makes the final decision or parents reach a custody agreement. The exact factors that the court considers vary, but there are some guiding principles that apply just about everywhere. Before you go to court or reach a settlement with the other parent, find out what the judge will consider to reach a final decision and how you can prove you're fit to parent.
Link to definition source