Reviews are matched against a fixed list of praise and complaint phrases per category. A review counts once per category and direction, however many phrases it hits. Keyword matching has known limits: a review saying "no chemical smell" matches an odour complaint phrase as well as a praise phrase, and rates in each direction are reported independently rather than netted off. The phrase lists are published in full below, and the same lists run against every brand.
Sources are bulk review feeds from Dreams, Bensons for Beds, Mattress Online, Eve, Mattress Next Day, Panda, Furniture Village and Emma. Percentages describe those reviews, not the mattresses themselves: "1.2% of reviews mention sagging" is a fact about the review base, and sample sizes are shown against every figure so you can judge the weight of each one. Spotted an error? Tell us and we will correct it. More on how the wider site rates products: how we test.
Durability: sagging and shape retention. Praise phrases: holds its shape, kept its shape, no sag, no signs of wear, still comfortable after, still feels new, still going strong, still like new. Complaint phrases: body impression, crater, dipped, dipping, gone soft, has sagged, lost its shape, sagg, sank, sunk.
Temperature: sleeping hot or cool. Praise phrases: breathab, keeps cool, keeps me cool, keeps you cool, nice and cool, sleeps cool, stays cool, temperature regul. Complaint phrases: get very hot, gets hot, overheat, sleep hot, sleeps hot, sweat, too hot.
Back pain and support. Praise phrases: back pain gone, back pain has gone, eased my back, great support, helped my back, helps my back, no more back pain, really supportive, so supportive, very supportive. Complaint phrases: back pain worse, bad for my back, hurt my back, hurts my back, not supportive, pressure points, wake up aching, woke up aching.
Odour and off-gassing. Praise phrases: aired out, no odour, no smell, smell disappeared, smell faded, smell went. Complaint phrases: bad smell, chemical smell, horrible smell, off-gas, smell lingered, smells bad, smelt bad, still smells, strong smell.
Firmness accuracy. Praise phrases: as described, exactly as described, firmness is perfect, just right, perfect firmness, true to firmness. Complaint phrases: firmer than expected, harder than expected, not as firm, softer than expected, too firm, too hard, too soft.
Value for money. Praise phrases: bargain, excellent value, good value, great value, value for money, worth every penny, worth the money. Complaint phrases: not worth the money, overpriced, too expensive for what, waste of money.
Delivery and service. Praise phrases: delivered on time, excellent service, fast delivery, great service, next day, on time, quick delivery. Complaint phrases: arrived late, damaged, delayed, delivery problems, never arrived, poor delivery, was late, wrong item.
