expression, adverb
ahead of others; slightly earlier; before someone else
Used when someone does something a little before others, often implying a head start or leaving earlier. Common in contexts of departure, action, or progress.
彼は一足先に帰った。
He went home a little earlier than the others.
一足先に会場に着いて準備を始めた。
I arrived at the venue ahead of everyone else and started preparing.
先に simply means 'before' or 'earlier' without the nuance of a small head start or leaving slightly before others. 一足先に emphasizes doing something just a step ahead.
Very similar in meaning, but 一足早く often focuses on the speed or earliness of an action, while 一足先に emphasizes the order or being ahead of others.
Compound of 一足 (ひとあし, 'one step') + 先に (さきに, 'ahead'). Literally 'one step ahead', used idiomatically to mean doing something slightly before others.