Dairy Milk Commercial 2002

In June 1905, in Birmingham, England, George Cadbury Junior made Cadbury's first Dairy Milk bar, with a higher proportion of milk than previous chocolate bars; by 1914, it would become the company's best-selling product. Through its development, the bar was variously called Highland Milk, Jersey Maid and Dairy Maid. Accounts on the origin of the Dairy Milk name differ; it has been suggested that the name change came about on the advice of a shopkeeper in Plymouth, but Cadbury maintains that a customer's daughter came up with the name. Fruit and Nut was introduced as part of the Dairy Milk line in 1926, soon followed by Whole Nut in 1930. By this point, Cadbury's was the brand leader in the United Kingdom. Almost a century on it has retained this position, with Dairy Milk ranking as the best-selling chocolate bar in the UK in 2014. In 2020 Dairy Milk was the second most popular snack overall in the UK behind McVitie's Chocolate Digestive biscuits.

In 1928, Cadbury's introduced the "glass and a half" slogan to accompany the Dairy Milk bar, to advertise the bar's higher milk content. In the early 2010s, Cadbury made the decision to change the shape of the bar chunks to a more circular shape which also reduced the weight.

Since 2007, Cadbury, has had a trademark in the United Kingdom for the distinctive purple colour (Pantone 2865C) of its chocolate bar wrappers, originally introduced in 1914 as a tribute to Queen Victoria. In October 2013, however, an appeal by Nestlé succeeded in overturning that court ruling.

In July 2018, Cadbury announced it would launch a new Dairy Milk version with 30% less sugar. The chief nutritionist of Public Health England, Alison Tedstone, said she was "pleased that Mondelez is the latest … name" to offer "healthier" products