Final answer:
The maximum number of levels that dark brown or black hair can safely be lightened is around 4 levels.
Step-by-step explanation:
The maximum number of levels that dark brown or black hair can safely be lightened depends on several factors, including the condition of the hair and the method used for lightening. On average, it is generally safe to lighten dark brown or black hair by up to 4 levels. Beyond this, the hair can become damaged and prone to breakage. It is important to consult a professional hairstylist for a personalized assessment and recommendation for lightening dark hair.