chesstempo has the best puzzles, but worst interface. chess.com and lichess both have ok puzzles and better interfaces. I prefer lichess, and sometimes go to c

chesstempo has the best puzzles, but worst interface. chess.com and lichess both have ok puzzles and better interfaces. I prefer lichess, and sometimes go to chesstempo for more focused work, but reasonable people can disagree. Also there are many books of puzzles.