On which language is Italian standard language based?

Tuscan, specifically its Florentine variety, became the language of culture for all the people of Italy, thanks to the prestige of the masterpieces of Dante Alighieri, Francesco Petrarca, Giovanni Boccaccio and Niccolò Machiavelli. It would later become the official language of all the Italian states and of the Kingdom of Italy, when it was formed. Only 2.5% of Italy’s population could speak the Italian standardized language properly when the nation unified in 1861.