Such a simple, yet important question to address. Having a clean yoga mat is essential to following the first niyama, saucha. Saucha means cleanliness or purity. In considering saucha and your yoga mat, use a sponge and a little mild detergent/soap (note, a “little”), hand wash with warm water. Again, use only a small amount of soap because any residue may cause your mat to become slippery when it is wet with perspiration. Some mats are machine washable but overtime they will wear down from the wash cycle. It’s best to handwash your mat regularly. Always hang/air dry which usually requires at least 12 hours (overnight) and do not fold or use your mat until it is completely dry. Happy cleaning!