Stand out with our endorsement

Our researchers scour the market for the right products to test, based on the selection criteria we've set for the product category. To make sure we stay impartial, we buy products before we test them.

Once we've done all our tests, we take the data, crunch it and translate into test scores that range from five stars to one, with each score rating a specific aspect of how that product performs.

Providers can't self-nominate – we decide who we select for assessment after researching the market to ascertain the aspects of a service that matter most to customers, which vary from service sector to service sector.

We use robust methods to analyse key aspects of a provider's service – which could include its policies, prices and terms & conditions – to see how they uphold key consumers rights and how well they meet the needs of customers.

We select from food and drink categories that are popular with mainstream shoppers and choose products that are easy to find in the big supermarkets, own-brand labels or otherwise.

Depending on the product we’re taste-testing, we invite a panel of shoppers or a panel of category experts to taste the products we've selected and score them against the key characteristics we've identified.

We started with products that people use regularly, like washing machines, tumble dryers, kettles, dishwashers and fridges. Now our list includes laundry detergents, headphones, rechargeable batteries, built-in ovens, steam irons, steam cleaners and more – and it's growing.

A product must be do more than just 'eco' for us to rate it as an Eco Buy – it must perform well in our tests to show us that it does the basics well, and its various test scores must lead to an overall test score of at least 60% for it to be considered.

The criteria we devise for each service category vary greatly depending on the nature of the category. But taking the energy sector as an example, we ask all the major domestic energy suppliers to give us comprehensive data about the electricity and gas they sell to homes, and we scour their websites to see how easy it is for shoppers to understand what they're buying and the environmental impact of their choices.

If a provider's eco rating meets or betters the eco benchmark we've set for its category, we name it an Eco Provider. We only recommend providers who meet or exceed our eco percentage benchmark for their service sector.

We use a list of staple items, including own-label and branded items that are sold by the big supermarkets, to run monthly price checks. From these we work out which supermarket offers the overall cheapest shopping basket in any given month.

With more and more shoppers struggling with rising prices, you can help them to manage their budgets by using our Cheapest Supermarket logo to show them you're the UK's cheapest supermarket of the year.

A Which? Great Value product tends to be a product that's at least 20% cheaper than the average price in its category, and that scores at least 60% against our Best Buy benchmark or at least significantly better than average.

Every year we survey thousands of consumers to ask them about the products they own. We use the information to determine which products are most likely to experience a fault, and how severe the fault is.