The best interests of the child refers to the factors most courts consider when making decisions on child custody and visitation rights.

These factors may include the needs and circumstances of the child (happiness, security, mental health, emotional development, educational opportunities, special needs, siblings, religious and cultural considerations, continuity and stability, child’s wishes) and the circumstances of the parent or caregiver (relationships, living arrangements, history of abuse, mental health, physical health, financial resources, substance abuse).

There is generally a presumption that it is in a child’s best interests to have a relationship with both of the child’s biological parents—unless one or both of the parents are shown to be unfit parents.

In California, the 'best interests of the child' standard is the guiding principle for courts when making decisions regarding child custody and visitation. This standard takes into account various factors to ensure the overall well-being of the child. These factors include, but are not limited to, the child's health, safety, and welfare; the nature and amount of contact with both parents; any history of abuse by one parent against any related child, the other parent, or a romantic partner; and the nature of the child's ties to school, home, and community. Additionally, if the child is of sufficient age and capacity to reason, the court may consider the child's wishes. California law does favor maintaining frequent and continuing contact with both parents, provided it is in the child's best interest. However, this presumption can be overcome if there is evidence that a relationship with a parent would be detrimental to the child's physical or emotional well-being. In cases where abuse, substance abuse, or other factors may impact a parent's fitness, the court will take these issues into account when determining custody and visitation arrangements.