Dark brown discharge and it's not a small amount. Can you help me please? No other symptoms.

Probably period. Dark brown vaginal discharge is usually old blood. Sometimes menstrual periods have more bleeding, and the discharge might be more obviously bloody. Sometimes the bleeding is slower and the blood stays a while in the vagina and turns brown. Often the discharge is more brown and less bloody at the beginning and end of the 5-7 day period. If possible pregnancy or infection, see doctor.