A practical way to think about sorting laundry is as a quick checklist to run through before starting the machine, rather than a fixed set of rules.
Check the labels first: Reading care labels on the pile tells you which items need cold water, which can handle hot, and which should be hand washed or dry cleaned only, so this becomes the first filter separating one group of clothes from another.
Group by colour intensity: Within what's left, separate very dark or newly dyed items from whites and light pastels, since even a small amount of dye bleeding can permanently discolour a lighter garment.
Group by fabric sturdiness: Heavy, rough-textured fabrics like denim or towelling should stay apart from soft or delicate ones like silk, chiffon or lace, since friction between the two during the wash cycle can pill, snag or thin out the more delicate fabric.
Balance the load: Finally, keep the total weight of each load reasonable rather than cramming everything in, and avoid mixing a couple of very heavy items, like a blanket, with several light ones, since an unevenly balanced drum washes less effectively and puts extra strain on the machine.
Therefore, sorting clothes before washing works best as a step-by-step check, starting from the care label, then colour, then fabric type, and finally the size of the load going into the machine.