Technically clump, but not very well.
The sand does clump in the litter box but the clump stays very wet and difficult to scoop. The moment you scoop, it falls apart into small wet smelly pieces and takes ages to remove. Since the pee stays wet, the litter box itself is also smelly even after cleaning. Might be suitable for one cat that doesn't pee very much but otherwise, very disappointing and I will not repurchase.