Is fish liver oil the same as cod liver oil?

"Pretty much. Cod liver oil has to come from the cod fish, whereas fish liver oil can come from any sort of fish."

Well, not really. Cod liver oil, as the name suggests, is usually extracted from cod fish livers. But fish oil is obtained by heating flesh or by-products (i.e., leftovers) of fish processing, leading to differences in quality of the oil.

Another major distinction - cod liver oil provides resources of vitamin A and vitamin D, in addition to Docosahexaenoic Acid (DHA) and Eicosapentaenoic Acid (EPA), which are widely known as Omega 3 fatty acids. Fish oil is a basic source of Omega 3.

Each have their own benefits, and choice should be made accordingly.