Is ONE PIECE episode 496 filler?
Canon No, episode 496 of ONE PIECE is canon.
#496
To The Sea Someday! The Pledge of the Three Brats!
いつか海へ！三人の悪童ちかいの盃！
Aired 1 May 2011
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.