Its strength varies by country, from about 20% to 28% — check the label; it changes how a Negroni tastes.
A little history
First made in the 1860s by Gaspare Campari; the recipe is secret, and its red came from cochineal until the mid-2000s in most markets.
Worth knowing
Negroni: equal parts gin, Campari and sweet vermouth. To batch, add about 20% water by volume and keep the bottle in the fridge — it pours ready to drink. A few drops of saline soften the bitterness without dulling it.