Is ONE PIECE episode 797 filler?
Canon No, episode 797 of ONE PIECE is canon.
#797
A Top Officer! The Sweet 3 General Cracker Appears!
大幹部! 三将星クラッカー登場
Aired 16 Jul 2017
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.