The overall Which? test score is made up of the following star ratings, all determined by our rigorous lab tests.
How we test stain removal
An overall rating showing how well the detergent removes a range of stains, such as drink stains (including wine and tea), food stains (including tomato purée, chocolate ice-cream, curry and mustard), make-up, everyday stains (including grass, mud, blood, ink and sweat) and grease, fat and oil stains.
How we test keeping whites bright
The brightness of white laundry after six washes in the detergent. The best detergents keep whites gleaming but the worst will start to turn them dull grey.
How we test preventing colour fading
The vibrancy of coloured fabrics after 20 washes in the detergent. Our test measures this on 14 different types of coloured fabrics.
How we test environmental impact
Whether these detergents contain chemicals that have any negative environmental effects. This includes whether they are biodegradable, harmful to aquatic life or persistent, which means the chemicals could linger and accumulate in waterways. In addition, we examine the packaging material to see whether it's recyclable or made from recycled materials and we also consider whether refills are available.