From ALttP Speedrunning Wiki
Quickhopping is a technique that allows Link to bypass all or part of the 20 frame countdown to jump off of a ledge.
It is performed by pressingas soon as Link hits the ledge collision. If pressing would result in a grab, then the quickhop will not happen. This is often the case when moving north. As such, turning left or right then pressing on the same frame or moving diagonally upwards while facing horizontally is the most reliable way to quickhop moving north.
In superspeed state, Link will quickhop immediately.