Broadly speaking, there are two different types of belly button: an ‘innie’ and an ‘outie’.
A protruding belly button is known as an outie and an estimated ten percent of the population has one. An outie occurs when the remains of the umbilical stump goes out instead of inwards. An outie belly button is nothing to be concerned about and does not cause any health issues.
An innie belly button, as the name suggests, is when the umbilical stump has gone inwards, creating a ‘well’ in the stomach. There are a number of different types of innie belly buttons. These include a vertical belly button (usually narrow and the most common type), a horizontal belly button (usually narrow), round (no hooding or covering), deep hollow (usually seen in people with excess abdominal fat) and lightbulb shaped (little hooding, a slightly oval shape that narrows at the bottom).
You are more likely to have an outie belly button if you have an umbilical hernia, a condition where the surrounding muscles don’t grow together properly causing the belly button to pop out, or an umbilical granuloma, which causes crusting on the belly button, making it appear bigger.