The UK Government's Childhood Obesity Plan aims to reduce consumer exposure to those food and drink products categorised as High in Fat Sugar Salt (HFSS)⁽¹⁾. From October 2022, new Regulations⁽²⁾ will restrict in-store and online promotion of HFSS products, classified as such using the UK Nutrient Profiling Model (UK NPM), by “location” (i.e., entrance, aisle) and by “volume” (i.e. multibuy).The aim of this research was to evaluate the current prevalence of HFSS products and their characteristics, including the presence of nutrition labelling, within entrance and multibuy promotions in online UK Supermarkets prior to implementation of the Regulations. An online survey of products featured within three UK supermarket entrance pages and multibuy promotions was undertaken between December 2021-January 2022. Data was collected for products in categories which were in scope of the Regulations (i.e., confectionery, ready meals etc.). Individual product webpages were each opened to manually record each product's nutrient content “per 100g” and the presence of any Front of Pack Nutrition Labelling (FOPNL). Using this information, computation of each product's UK NPM scores was performed. Prevalence of HFSS products (proportion which scored ≥4 in the UK NPM) and those which displayed FOPNLs were calculated and variations according to promotional type, product category and retailer were evaluated using chi-squared tests. Overall, 625 products were audited across three online supermarkets which encompassed 523 products on multibuy promotions and 102 from entrance promotions. A total of 37% of multibuy-promoted products were categorised as HFSS. Of these, 95% of multibuy-promoted confectionery products were HFSS (n = 168), 18% of soft drinks (n = 83), 7.3% of yogurts (n = 110) and 6.1% of ready meals (n = 162). In entrance promotions, 72% of in- scope products were categorised as HFSS. Variations in proportion of HFSS products was found by retailer (ranging from 49% to 92%) as well as by promotional type, with entrance promotions almost twice as likely to contain HFSS than multibuy promotions (χ² (1) = 42.0, p < 0.005). Entrance-promoted products were also less likely to show FOPNL on product webpages than multibuy promotions (48% vs 74% respectively, χ² (1) = 27.7, p < 0.005). This study provides evidence that HFSS products which are in scope of the new Regulations are currently promoted in UK supermarket websites, with variations in prevalence seen across retailers, promotional type and product category. Findings reflect recent work on in-store “meal deals”⁽³⁾, which also find price promotions on products categorised as HFSS.Findings contribute baseline data to support the future post-implementation evaluation of these new Regulations and their impact on the prevalence HFSS products on promotion in UK online supermarkets.