Ketchup, or catsup, is a table sauce.
Traditionally, different recipes feature ketchup made of egg white, mushrooms, oysters, mussels, walnuts, or other foods but in modern times the term without modification usually refers to tomato ketchup, often called tomato sauce in the United Kingdom and Ireland.
It is a sweet and tangy sauce, typically made from tomatoes, a sweetener, vinegar, and assorted seasonings and spices.
Seasonings vary by recipe, but commonly include onions, allspice, cloves, cinnamon, garlic, and sometimes celery.
Heinz tomato ketchup is the market leader, with an 82% market share in the UK and 60% share in the US. (source)
So can hamsters eat ketchup?
It is not easy for hamsters to eat and so is not the best food to feed them.