Many types of cheese are similar to Gruyere cheese and can be used as substitutes, including Swiss cheese. A generic Swiss cheese works in place of Gruyere in almost any type of application.
Another type of cheese that is similar to Gruyere cheese is Emmental, which is best used when substituting for Gruyere when making fondue.
If the cheese is to be melted on top of a dish, Jarlsberg makes a good substitute for Gruyere. Comte, Beaufort and Raclette can also be used in place of Gruyere.
Gruyere cheese is classified as a hard cheese and, when aged for long periods, offers an earthy taste and grainy texture.