The dark “vein” in shrimp is actually its digestive tract, not a blood vessel. It’s safe to eat, but can contain grit or partially digested food that affects taste and texture.
Deveining is optional: for large shrimp or dishes where presentation matters, removing it gives a cleaner look and smoother bite. For small shrimp in soups or stir-fries, many cooks skip it entirely.
Knowing what it is helps you decide confidently whether to remove it or not.