It is haram.
There are many food products which may not appear to be what they are or are made of, and it is very easy for the uninitiated to be mistaken.
Gelatin is a mixture of peptides and proteins produced by partial hydrolysis of collagen extracted from the skin, bones, and connective tissues of animals such as domesticated cattle, chicken, pigs, and fish.
Even some fruit or vegetarian products are not what they seem to be because of the additional ingredients added. For example, Omega-3 which is made of fish oil is added to orange juice so that you can drink it to your heart’s content because apparently Omega-3 is good for your preventing heart disease. So, do check the ingredients and the fine print if you are concerned with what you eat.