Potty training liners are a comfortable, child sized, absorbent liner, with a concave center and an expandable, flexible bottom to allow rapid flowing urine collection and retention. The Liner has unique absorbent collapsible side walls with an unobstructed center containing superabsorbent for quick pooling of urine. The liner is adhered to the inside of the child's underwear with a thick adhesive strip on the bottom outer portion of the liner. The Liner is soft and flexible, and does not have the feel of a diaper. It is a unique stop-gap solution for children progressing from pull-on diapers to unprotected underwear. The purpose of the liner is for training, and short term emergency "accident" protection, as opposed to long term wearable protection.