The manufacture of a chocolate bar from raw cocoa ingredients requires many steps, from grinding and refining, to conching and tempering.

The 19th century saw the emergence of the modern chocolate industry; most manufacturing techniques used today were invented during this period.

Ingredients not derived from cocoa have been added to bars since the beginning of the chocolate industry, often to reduce production costs.

[4][5] Solid chocolate was probably already consumed in pre-Columbian America, in particular by the Aztecs, despite the beverage being the traditional form of consumption of cocoa in Mesoamerica.

[8] Dominican friar Diego Durán mentions in his writings that Aztec soldiers carried small balls of ground cocoa among other military rations.

Chocolate was usually sold as a solidified ground but still grainy cocoa paste (in the form of blocks, sticks or balls) to be dissolved in water or milk, either plain or already sweetened and flavoured.

[11][12] It is unclear when bars or tablets of chocolate (meant to be eaten straight as a candy rather than grated into a drink) were made for the first time.

The Marquis de Sade wrote to his wife in a letter dated May 16, 1779, complaining about the quality of a care package he had received while in prison.

Up to and including the 19th century, confectionery of all sorts was typically sold in small pieces to be bagged and bought by weight.

The introduction of chocolate as something that could be eaten as is, rather than used to make beverages or desserts, resulted in the earliest bar forms, or tablets.

[17] Among the pioneers were Joseph Storrs Fry, who patented a method of grinding cocoa beans using a Watt steam engine in 1795,[18][19] and Poincelet, who invented the melanger in 1811, soon adopted by most chocolate manufacturers.

[25] 1828 is the year of a major breakthrough: Casparus van Houten[26] patented an effective method for pressing the fat from roasted cocoa beans.

[29][30] An American magazine from 1836 notes that (small and sweetened) chocolate bars have become popular in France for their nutritious quality and portability.

[30] In 1849, both Fry and Cadbury chocolates were displayed publicly at a trade fair in Bingley Hall, Birmingham.

Tempering allows the production of chocolate that is perfectly hard at room temperature and that have an attractive shiny appearance.

In 1897, following the lead of Swiss companies, Cadbury introduced its own line of milk chocolate bars in the UK.

[52] In the United States, immigrants who arrived with candy-making skills drove the development of new chocolate bars.

[53] Milton S. Hershey, a Pennsylvania caramel maker, saw a German-manufactured chocolate-making machine at the 1893 Chicago World's Fair.

[11] Producers soon began combining chocolate with other ingredients such as nuts, fruit, caramel, nougat, and wafers.

[58] Additionally, the overwhelming majority of combination bars use milk chocolate, which further decreases the amount of cocoa in the finished product.

[69] In addition to these main ingredients a solid chocolate bar may contain flavorings such as vanilla and emulsifiers such as soy lecithin to alter its consistency.

[73] The world's largest chocolate bar was produced as a stunt by Thorntons plc (UK) on 7 October 2011.

[74] On January 16, 2020, Mars Inc. received the Guinness World Record for largest chocolate nut bar.