Background Snacking is associated with a higher daily energy intake and dietary guidelines recommend snacks of no more than 200 kcal for adults and 100 kcal for children. The present study examines the energy content, nutritional quality and price of single-serving snack food products sold by major supermarket and coffee shop chains in the UK. Methods Energy content, nutritional content and price of single-serving snack products were recorded in 2019 via the websites of 14 major chains (seven supermarkets; seven coffee shops). Results The mean energy content of all eligible snack products (n = 2283) was 186 kcal [95% confidence interval (CI) = 182–190]. The mean energy content of the snack products sold at coffee shops (n = 379; 282 kcal [95% CI = 269–295]) was significantly higher than the energy content of the snack products sold at supermarkets (n = 1904; 167 kcal [95% CI = 164–170]). Seventy nine % of supermarket snacks exceeded energy recommendations for children and 32% for adults. In coffee shops, 91% exceeded recommendations for children and 73% for adults. Forty one % of snacks were high in fat, 42% were high in saturated fat, 39% were high in sugar and 7% were high in salt. Cheaper snack products were more likely to be of lower nutritional quality. Conclusions The high proportion of snack products that do not meet public health recommendations for energy content may contribute to the association between snacking and increased energy intake. Public health measures to increase the availability and reduce the price of snack products that meet public health energy content recommendations may reduce population-level obesity.