Universal donor blood group is :

The people with blood group O can donate blood to anyone, and are called universal donors. This is because the red blood cells in O blood group don’t have any surface antigen . So, in the recipient blood, no antibodies are formed in response making it safe for transfusion.

Blood group A has antigen A, blood group B has antigen B and blood group AB has both antigens A and B. All these types of blood groups will produce antibodies in the recipient blood.