Probably worm drive.
But this is why you should always carry an easy to start dependable chainsaw with a long bar for self defense. Sometimes there isn’t an extension cord handy.
Thirty years ago, I was working for my brother, a Philadelphia area contractor. We had a guy working for us who used to wedge the guard open on the worm-drive saw. He was cutting through a board when the saw bound and kicked back. The blade, at full depth, went across his left thigh. We saw it happen, and it was gruesome. He made a full recovery.