Your score is your final ladder’s steps plus one for every hint and one for every undo. The lowest score wins, and par is the best you can do.
Open Word Ladder with the daily challenge to get today’s pair, the same for everyone. Your score is the number of steps in your final ladder, plus 1 for each hint and 1 for each undo. A perfect run, with no hints and no undos, scores par (what par is).
The lowest score ranks first. You get one scored ladder a day: it locks when you reach the last word, and a new pair arrives at midnight UTC. The server replays your steps to work out the score, so the ranked score is always the one it computed.
See also What a hint shows. For tips, read the Word Ladder tips and strategy.