Abstract: The jar lid loosening device includes a pair of jaws which are arranged to compress upon a lidded jar inserted therebetween. Of the pair of jaws, one jaw is a passive jaw and the other is the active jaw. The passive jaw is fixed substantially stationary and hence it neither twists nor travels in compression or retraction. The active jaw, in contradistinction. is given compound motion. More particularly, the active jaw is mounted in a traveling head. The traveling head is arranged to cycle through compression and retraction strokes. The active jaw is carried in the traveling head such that, generally, the active jaw rides passively along with the traveling head through the compression and retraction strokes. If however, a lidded jar is inserted between the jaws, then during a compression stroke the active jaw eventually limits out against the lidded jar. From then on, the lidded jar is subjected to increasing compression between the jaws by virtue of the traveling head.