Salmiakki's main ingredients are liquorice root and ammonium chloride (NH4Cl.) which is also called salmiak or salmiakki.

Many agree that it is an acquired taste and is not generally appreciated outside of certain parts of Europe in a similar manner that Marmite is loathed outside of the United Kingdom.

Only candies containing NH4Cl as one of the main ingredients can be called salmiakki; salty liquorice candy without ammonium chloride is called lakritsi in Finnish, lakrits in Swedish, lakris in Norwegian, lakrids in Danish or zoute drop in Dutch. Although salmiakki candy resembles salty black liquorice in colour, it is flavoured with the salt ammonium chloride and often also mixed with liquorice. The word salmiak(ki) comes from the old Latin name for ammonium chloride, sal ammoniac. In Finland Salmiakki was once a trade name of Fazer, but became quickly a genericized trademark not unlike nylon.

Salmiakki candies are almost always black or very dark brown and can range from very hard to very soft and may be brittle. The other colours used are white and variants of grey. Since pure ammonium chloride is a white powder, the reason why black is the preferred colour for salmiakki is somewhat unclear. It might be partly to provide a "tougher image" for the candies, and partly because of the liquorice used to vary and soften the salty flavour. Carbon black is used as a food colouring agent in these candies. Conversely, pure ammonium chloride is sometimes referred as raakasalmiakki (raw salmiakki).

The canonical shape for salmiakki candies is a four-cornered, diamond-shaped lozenge. This shape is so popular that in Finnish, the word "salmiakki" can sometimes refer to this shape, instead of the candy or the salt it is produced with. For example, Finnish Defence Forces reservist officer students rank insignia are known as "salmiakki"s for their distinctive shape.

Round salmiakki candies are also very common, either disc-shaped or complete spheres.

In addition to being used in candy, salmiakki is also used to flavour vodka, distilled rye brandy, ice cream, cola drinks, and recently, meat ("Salmiakkipossu" is a brand of salmiakki-flavoured pork, probably named as a pun on "Salmiakkikossu", meaning salmiakki Koskenkorva). Salmiakki is also a popular ingredient for home-made dip sauces for potato chips.

Salmiakki is extremely popular in all five of the Nordic countries. It is uncommon outside Europe, but can be found in many delicatessens as well as in the Swedish furniture store IKEA that capitalizes on its Swedish image by selling a small selection of Swedish foods in addition to furniture in many markets.

Typical examples of Salmiakki candy:
Tyrkisk Peber & Pantteri Duo