Darkvision

A creature with darkvision can see in normal, dim light, and darkness; some forms of magical darkness may specify they obscure vision even to those with darkvision. Darkvision specifies a distance a creature can see in which they treat as if it were normal light. Creature’s sight in darkness is devoid of color, and colors may be difficult to discern or muted in such conditions.

Multiple sources of darkvision may stack, but only add half of the lower of the two values to the higher darkvision distance.