What kind of oranges are used in marmalade?

Marmalade is typically made using Seville Oranges, known for their tartness and high pectin content, which helps the preserve set properly. These oranges are favored for their bright flavor and aroma, making them ideal for the sweet and tangy profile of marmalade. Other varieties, such as navel or blood oranges, can also be used for different flavor nuances, but Seville oranges remain the traditional choice.