Which One Piece episodes are filler?

One Piece's filler share is low for a series of its length because Toei mostly chose pacing over invention, stretching canon rather than replacing it, which is why this list is short and why the pacing discussion in the Library's anime vs manga page matters more to most viewers than this page's episodes. The filler that exists clusters in safe harbors, between arcs, where a self-contained story cannot collide with Oda's plans.

G-8 is the standing exception to every skip list. The ten-episode arc after Skypiea, in which the crew must escape the Marine fortress Navarone and its commander Vice Admiral Jonathan, is anime-original and is routinely ranked among the series' best arcs outright, filler or canon. The Library's position is the fandom's: skip by list if you must, but watch G-8. The Foxy material carries a different warning: the anime expanded the Long Ring Long Land arc and moved pieces of it, so its episodes mix canon and invention inside single episodes.

Two categories are not filler and should not be skipped on a filler list's authority: the cover story adaptations, rare and partial as they are, and the film tie-in arcs, which are original but were made with the films' staff and Oda's supervision to lead into Strong World, Film Z, Gold, and Red respectively. Episode of Luffy and the other television specials are their own class, recaps and side stories sold as events.

For physical media buyers, filler knowledge prices the Log Collection and season sets correctly: episode counts alone mislead, because a set's value to a manga reader depends on how much of it adapts chapters. The Library's Log Collection page gives the television version's own collecting logic.