Chocolate bars including famous brands such as Kit Kat, Yorkie and Aero will contain 10% less sugar by next year, manufacturer Nestle has announced.
The sugar will be replaced with higher quantities of existing ingredients or other, non-artificial ingredients, and the amount of calories will be limited.
It means about 7,500 tonnes less sugar will be used to make the confectioner's products by 2018.
Nestle said it could help to have a significant impact on public health.
Fiona Kendrick, chairman and CEO of Nestle UK and Ireland, said: "Our confectionery brands have been enjoyed in the UK for more than a century and we know that if we can improve these products nutritionally, provide more choice and information for the consumer... we can have a significant impact on public health.
"Nestle is at the forefront of efforts to research and develop new technology that makes food products better for our consumers.
"These innovations will help us to reduce sugar in confectionery when they are combined with other, more common methods like reformulating recipes and swapping sugar for other, non-artificial ingredients.
"Making these improvements to our products is key to us delivering better choices for our consumers while retaining the same great taste that they know and love."
Last year, Nestle said its researchers had made a scientific breakthrough by discovering a way to structure sugar differently so 40% less is used.