Diet Pepsi is a diet carbonated cola soft drink produced by PepsiCo, introduced in 1964 as a variant of Pepsi with no sugar. First test marketed in 1963 under the name Patio Diet Cola, it was re-branded as Diet Pepsi the following year, becoming the first diet cola to be distributed on a national scale in the United States. In the 1960s and 1970s its competition consisted of Tab, produced by The Coca-Cola Company, and Diet Rite cola, produced by RC Cola. While the U.S. represents the largest single market for Diet Pepsi, it was launched in the UK. History Diet Pepsi was originally test marketed in the United States under the name Patio in 1963. Following a positive reception attributed to the shifting dietary habits and preferences among the Baby Boomers at the time, the drink was launched nationally as Diet Pepsi the following year. It became the first diet cola to be distributed on a national scale in the US. Distribution was extended to the United Kingdom in 1983, where it is also referred to as Pepsi Diet. Distribution has since expanded to other countries around the world; though an alternate name is used in certain countries. In Italy, Czechia, Poland, Argentina, Spain Greece, Turkey, Russia, Ukraine, and Brazil, the beverage is known as Pepsi Light. Diet Pepsi competed primarily with The Coca-Cola Company's Tab in the 1960s and 1970s; however, The Coca-Cola Company introduced Diet Coke in 1982, which has since been the principal competing product to Diet Pepsi. As of 2010, Diet Pepsi represented a 5.3 percent share of all carbonated soft drink sales in the United States, and was ranked as the #7 soft drink brand by volume. In the same year, Diet Coke was recorded as having a 9.9 percent market share. In December 2012, an AP article reported that Diet Pepsi was changing its sweetener to sucralose ahead of a major rebranding of the soft drink set for January 2013. In 2015, some people on Facebook and Twitter expressed their distaste for the new formula. In response, Pepsi revived its aspartame formulation, as "Diet Pepsi Classic Sweetener Blend" for US markets in September 2016, and it was sold alongside the new formula. PepsiCo later announced plans to revert Diet Pepsi's sweetener from sucralose to aspartame. The new formulation was released marketwide on February 25, 2018. Flavor variations Additional variations of Diet Pepsi have