Aldi has knocked Waitrose off the top spot as the UK's favourite supermarket for in-store shopping.
Customers rated their experience at the budget retailer as best in Which?'s annual survey.
Respondents rated Aldi's value for money very highly, and were positive about its own-label products and range of fresh produce.
“With food costs rising it seems as though shoppers have felt the pinch and are voting with their feet and wallets," said Alex Neill, managing director of Which? home products and services.
This comes just a few weeks after Aldi and Lidl were both named some of the UK's best brands for the fourth year running by YouGov.
But customers were less satisfied with staff availability in Aldi and Lidl stores compared to M&S and Waitrose, which both scored highly on this front.
Meanwhile, shoppers were most pleased with Iceland and Ocado when it came to online grocery buying.
Iceland was rated as better value for money, but Ocado had a better range of products. Both are top-rated for convenient delivery and the service provided by drivers.
Although Morrisons was the joint third-best online supermarket, the big four supermarkets were generally rated worse than their rivals. Asda was judged to be the worst online supermarket while in-store experience at Sainsbury's was rated lowest.
Neill added: “The big four supermarkets need to up their game or risk losing their customers to other supermarkets who are doing a better job of giving people what they want.”