I want to watch Bleach, but the anime has a lot of filler content not in the manga. I’d rather not watch the filler content and only watch the episodes which are directly related to the plot. To be clear, I’m defining a filler episode as one which is not based on any story in the manga or based on extra manga chapters which have nothing to do with the overarching story.
Which episodes are filler?
The following episodes are anime-original content which you should skip if you aren’t interested in filler. Some of the other episodes include original elements or reference events from filler episodes, but these do not impact the story in the long run so you can safely ignore them. The ones based on manga omake are noted as such.
Compactly, the fillers are: 33, 50, 64-109, 128-137, 147-149, 168-189, 204-205, 213-214, 227-266, 287, 298-299, 303-305, 311-342, 355. In more detail:
Episode 33 Miracle! The Mysterious New Hero (奇跡！謎の新ヒーロー) (based on “Karakura Heros” Omake 1)
Episode 50 The Reviving Lion (よみがえる獅子) (based on “Karakura Heros” Omake 2)
Episodes 64-109 Bount Arc
Episodes 128-137 Stolen Hogyoku arc
Episodes 147-149 Forest of Menos Subarc
Episodes 168-189 Captain Shuusuke Amagai Arc
Episode 204 Ichigo’s Stomach-cutting Persuasion Strategy (一護の切腹説得大作戦☆)
Episode 205 Thump! A Kemari Tournament Filled with Hollows (ドキ！虚だらけの蹴鞠大会)
Episodes 213-214 Karakuraizer Mini-arc (based on sketches from volume 29)
Episode 227 Wonderful Error (ワンダフル・エラー) (based on Omake 0.8 “A Wonderful Error”, 0.side-A “The Sand”, and 0.side-B “The Rotator”)
Episode 228 Summer! Sea! Swimsuit Festival!! (夏だ！海だ！水着祭!!) (based on Omake BLEACH on the BEACH!!)
Episode 229 Cry of the Soul? The Rug Shinigami is Born! (魂の叫び？ヅラ死神誕生！)
Episodes 230-265 Zanpakutou Unknown Tales arc
Episode 266 Ichigo vs. Ulquiorra, Resume (一護ＶＳウルキオラ、再開!) (recap episode)
Episode 287 Side Story…Ichigo and the Magic Lamp (外伝！一護と魔法のランプ)
Episode 298 Film! Festival! Shinigami Film Festival! (映画だ！祭りだ！死神映画祭！)
Episode 299 Theatre Opening Commemoration! The Hell Verse: Prologue (劇場公開記念！地獄編・序章) (adapts “Imaginary Number 01: The Unforgivens” Omake)
Episode 303 Real World and Shinigami! The New Year Special! (現世も死神も！お正月スペシャル！)
Episode 304 Another Side Story! This Time’s Enemy Is a Monster!? (外伝再び！今度の敵はモンスター！？)
Episode 305 Delusion Roars! Hisagi, Towards the Hot Springs Inn! (妄想爆走！檜佐木、温泉旅館へ！)
Episodes 311-316 Miscellaneous Fillers (none of these are based on manga chapters so I’ve grouped them together)
Episodes 317-342 Gotei 13 Arc
Episode 355 Shinigami at War! New Year in Seireitei Special! (死神参戦！瀞霊廷もお正月ＳＰ！)
The series ends with episode 366, at which point you can pick up from manga chapter 480 if you so choose.
The sources for this are scattered across a number of sites, but of particular note are Bleach Wiki, Wikipedia’s list of Bleach episodes, and this MAL forum post. However, all had at least some errors so I’ve had to check on various other websites as well.