Cold sores are very contagious but canker sores are not contagious even during oral.
The cold sore is caused by the herpes simplex virus while the canker sore is caused by a variety of things such as Injuries to the mouth, acidic or spicy foods, vitamin deficiencies, hormones, stress, or autoimmune disorders.
Cold sores occur on the outside of the mouth while canker sores occur on the inside of the mouth.
Canker sores and cold sores are often confused with each other but canker sores which occur inside the mouth are not contagious but cold sores which occur on the outside of the mouth are contagious.