Dinghy designs are often referred to as "classes"; these classes are usually categorised as one design, open, or restricted. A more formal term for open is "Development Class". One design dinghies are supposed to be identical, though in reality this is not always the case. Only the most restrictive one design classes will restrict individual fittings. Then there becomes a sliding scale of allowable modification or design differences; restricted classes would typically allow the movement of fittings or even parts of the boat around, but are unlikely to allow major changes to hull shape or sails. Truly open development classes are also almost unknown, the famous line about the 18ft skiff "the boat shall be 18ft long and the race starts at 2 o'clock" is a myth but open classes will usually allow pretty radical changes within usually some kind of box rule which specifies depth, length, width of hull height of mast and sometimes a minimum weight and sail area.

Classes which are not development classes are usually referred to as "One design". The idea is that One Designs provide a fair and level playing field for even competition, where as Development Classes drive boat speed and technology forwards. The first one design was the Water Wag designed by Thomas Middleton, which first sailed in Dublin Bay in 1887. The class is still sailed today, well over a hundred years later.

Skiffs are the fastest and arguably most difficult type of dinghy to sail. A skiff has a flat narrow hull with a disproportionately large sailplan, usually consisting of an asymmetric spinnaker, blade jib and fully battened main. Sailors manage the rig with the use of racks (wings) and trapeze. Examples are the 49er, an Olympic boat, 18 Footers (see below) and the advanced International 14.

High Performance dinghies are fast and powerful dinghies designed for racing around an Olympic triangle (Olympic Racing Course). Examples of such dinghies are the International Flying Dutchman, the International 505, the Jet 14, the Fireball, the Osprey, the Javelin and the International 470. They can all plane easily, even upwind and they use trapeze and a symmetric spinnaker. Not all are two handed boats: the International Contender and the RS600 are high performance single handed boats equipped with a trapeze, but not a spinnaker, and demonstrate a comparable performance. Skiffs are usually classed as High performance dinghies.

Racing dinghies are designed for racing, but not all have necessarily the same calibre of performance as the above. However in many cases they can still offer equally close competition, at the very highest standards, which for many racing helmsmen and crews is the most important consideration. They cover a wide range, and many are descended from Uffa Fox's seminal International 14. People often "travel" with their dinghies to international races in famous sailing spots such as Lake Garda in Italy. The Snipe International Class still stands as one of the strongest classes, after reaching the status of world's largest fleet of dinghies in July 1936. Other examples include the GP14, Enterprise, Solo, Graduate, Firefly, Lark.

Cruising inghies are designed for leisure and family sailing and are usually more stable than high performance dinghies. This is provided by a 'chined' (less rounded) hull, greater displacement, and proportionally smaller sail area. Some are specifically designed for longer passage-making, and/or for camping aboard.Classic dinghies are typically used as yacht tenders or shore boats, and emphasize beauty and versatility over sailing performance. Although many are still made entirely from wood, the majority of the most popular classic sailing dinghies combine a fiberglass hull with enough finely finished teak or mahogany to represent the "best of two worlds" approach. Examples of classic sailing dinghies are Minto, Fatty Knees, Trinka, Bauer, Whitehall and Gig Harbor.