Cod liver oil is a supplement that contains omega-3 along with vitamin A and D, whilst omega-3 supplements by themselves typically will only contain omega-3.
Both omega-3 and cod liver oil supplements contain the important fatty acids which help you to maintain a healthy heart, amongst other benefits.
If you’re taking omega-3 supplements, the NHS recommends that you should avoid cod liver oil as you’d be taking more than what your body needs to function as it should.
If you’re looking to reap the benefits of other vitamins as well as healthy fats, cod liver oil might be for you - you should stay clear if you’re pregnant, however, as too much vitamin A can be very harmful to your baby.