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If you’ve ever been deep into Naruto or Bleach and suddenly found yourself watching characters play volleyball on a beach with zero relevance to anything that came before it, you’ve encountered filler. It’s one of the most complained-about things in all of anime, and also one of the most misunderstood. Here’s what’s actually going on.

What even is a filler episode?

The simplest definition is this: a filler episode is any episode that doesn’t come from the original source material and isn’t part of the main canon story. Interestingly, most anime aren’t original productions. They’re adaptations of manga, light novels, or visual novels written by someone else, and that source material is the blueprint the studio works from. When that blueprint runs out, studios usually have two choices. They can either pause the anime and wait for the author to write more, or keep the show running by producing their own original content in the meantime. Thus, that original content is filler.

It’s worth knowing that the term gets used loosely. Technically, any content not found in the source material qualifies, which means a Bleach action filler arc and a Naruto beach comedy episode are both filler despite feeling nothing alike. What connects them is that neither one actually happened in the manga, and when the main story resumes, neither one is ever mentioned again.

Why studios do it

The core reason is simple: popular anime air weekly, and manga chapters come out weekly too. The problem is that animating a chapter takes significantly more time and resources than writing one. A manga artist can produce a chapter in a week. Turning that same chapter into animation with voice acting, music, and movement takes a team of people several weeks minimum. The anime catches up to the manga faster than anyone wants it to, and stopping a weekly show cold is a commercial and logistical nightmare.

There’s also a financial side to it that rarely gets discussed. Weekly anime during the era of Dragon Ball, Naruto, and Bleach were massive commercial engines. Merchandise, licensing deals, and advertising revenue were all tied to keeping the show on air every single week without interruption. A hiatus, even a short one, could mess with the broadcast schedule, hurt audience momentum, and throw off merch and ad revenue. Because of that, long-running anime often leaned on filler or slower pacing just to keep the show airing week after week instead of going off the air entirely.

The infamous examples

Naruto is the most referenced case for a reason. Out of 720 episodes across the original series and Shippuden, roughly 41% is filler. Studio Pierrot was adapting Masashi Kishimoto’s manga in real time while it was still being written, and the gap between what the anime needed and what the manga had available kept widening. The result was entire arcs, sometimes dozens of episodes long, that went nowhere and are largely forgotten today.

Bleach followed the same pattern with Studio Pierrot at the helm again, inserting full original arcs between canon story beats. In fact, the series has even more filler episodes than Naruto, with about 45% of its episodes considered non-canon. One Piece is the longest-running example still active, though Toei Animation has increasingly opted for slower pacing of canon material rather than outright filler.

Then there’s the Endless Eight from The Melancholy of Haruhi Suzumiya, which is a different beast entirely. Eight nearly identical episodes covering the same two weeks of a time loop, produced by Kyoto Animation, clearly as an artistic statement rather than a budget problem. Fans were furious. Whether it was brilliant or insufferable depends entirely on who you ask.

Are all fillers actually bad?

Not even close. The reputation comes from the worst examples, but filler done well can genuinely add to a series. Some of the most beloved moments in Naruto are technically filler, including the Kakashi Anbu arc, which explored a character the main story never had time to dig into properly. Fullmetal Alchemist’s 2003 adaptation diverged from the manga entirely once it ran out of chapters, producing a completely original second half and a film conclusion that some fans still prefer to Brotherhood.

Filler also gives secondary characters room to breathe. Main storylines in long-running shonen are usually too plot-driven to slow down for character work outside the main cast. Filler episodes, whatever their reputation, sometimes do exactly that.

Why modern anime uses less filler

The seasonal model changed everything. Rather than producing 50 episodes a year on a weekly broadcast schedule, most anime now air in chunks of 12 or 13 episodes per season, pausing between cours to let the source material stay ahead. That structure greatly reduces the pressure that created filler in the first place. Jujutsu Kaisen has zero filler episodes. Attack on Titan has zero. Demon Slayer has zero. The model they operate under simply doesn’t require it.

Streaming also shifted audience expectations. Viewers who binge shows have far less patience for placeholder content than audiences who waited a week between episodes, and studios know it.

The bottom line

Filler episodes exist because the economics of weekly anime made them necessary for a long time, and because stopping a popular show mid-run was simply not an option studios were willing to take. The seasonal model has made them largely obsolete, which is why newer fans sometimes don’t even know what filler is until they try to watch something from the early 2000s and hit episode 97 of 220 consecutive non-canon episodes. It’s a product of a specific era in anime history, and understanding that context makes it a lot easier to appreciate why it happened without pretending it was ever a good viewing experience.

Call anime a cartoon in front of the wrong person, and you’ll hear about it for the next twenty minutes. But the question itself is actually worth taking seriously, because the answer is genuinely more complicated than either side of that argument usually admits. Here’s a proper breakdown.

What does “anime” actually mean?

Starting with the word itself, because this is where most people get tripped up. In Japan, “anime” is simply a shortened form of “animation” (アニメーション). That’s it. Japanese people generally use it to describe animation in a broad sense, without it being strictly limited to domestic or foreign origin. The word itself doesn’t carry a special “exported Japanese style” meaning inside Japan, the way it does in the West.

The key difference comes later. The term “anime” was borrowed from Japanese into English during the late 20th century, where it became specifically associated with Japanese-produced animation. So while in Japan it refers to animation as a medium in general, in Western usage it became a label for animation from Japan or strongly Japanese-influenced works.

So technically, in its original Japanese context, anime is just a form of animation, which places it in the same broad category as cartoons. The distinction is mostly about cultural usage rather than the medium itself.

So, is it technically a cartoon?

Technically, yes. Both cartoons and anime are animated. Both use storyboarding, voice acting, character design, and frame-by-frame production. In English usage, anime is commonly defined as “a style of Japanese animation,” which makes it a subcategory of animation rather than a completely separate medium. The argument that anime isn’t a cartoon at all is more about cultural distinction and interpretation than a strict technical definition.

That said, calling anime just a cartoon is a bit like calling a graphic novel just a comic book. Accurate in a technical sense, but it flattens a lot of meaningful distinctions that actually matter when you’re talking about what the medium does and who it’s for.

What actually makes anime different?

In the West, animation became closely associated with children mainly due to television economics and production models, not censorship codes. The Hays Code regulated live-action film, not animation, and the Comics Code Authority applied to comics, not animation. The shift toward kids’ content came largely from cheap TV production formats like Hanna-Barbera shows and the rise of syndication, scheduling, and merchandising.

Japan did not have a single centralized censorship system like Hollywood, but anime is still subject to fragmented regulation through broadcast standards, publisher oversight, and obscenity laws. The difference is structural rather than the absence of rules.

Western cartoons historically leaned toward episodic storytelling with resets because of syndication-friendly TV models. However, this is not universal. Modern Western animation often uses serialization, such as Avatar: The Last Airbender or Arcane.

Anime, influenced heavily by manga serialization, tends to favor long-form continuity where characters and plots evolve over time. Still, anime is not inherently serialized, and many shows are episodic.

The visual identity of anime was strongly shaped in the TV era by Osamu Tezuka’s Astro Boy, which popularized limited animation techniques to reduce production costs, such as fewer frames and reused assets. However, these methods were not exclusive to Japan or invented by Tezuka alone. Similar techniques existed earlier in studios like UPA in the United States and in broader TV animation economics.

What became “anime style” was the result of production constraints turning into a consistent visual language, including static framing, expressive close-ups, and selective motion rather than full cinematic animation.

The grey area: Avatar, RWBY, and the shows that break the rules

Here’s where the debate gets genuinely messy. Avatar: The Last Airbender looks like anime, feels like anime, uses serialised anime-style storytelling, and was heavily influenced by shows like Cowboy Bebop and Princess Mononoke. Its creators have said as much in interviews. But it was produced by Nickelodeon Animation Studios in the United States, which, by the strictest definition of the word, means it is not anime. Thus, the series is often categorised as “anime-influenced animation,” which is probably the most honest label available.

Now, the same applies to RWBY, Teen Titans, and Voltron: Legendary Defender. These shows absorbed anime’s DNA without being produced in Japan, and whether that makes them anime or not depends entirely on which definition you’re using.

The creator of RWBY, the late Monty Oum, expressed the view that calling anime exclusively a Japanese art form is a narrow way of thinking and that it can be better understood as an art form defined by style and creativity rather than nationality. Not everyone agrees with that perspective, and the debate is still very much alive.

So, what’s the actual answer?

Anime is a specific style of animation that originated in Japan, developed its own distinct visual language, storytelling traditions, and cultural identity, and now operates as its own recognised medium with its own industry and global audience. Calling it a cartoon isn’t wrong in the strictest technical sense, but it misses everything that actually makes it what it is.

The better way to think about it: all anime is animation, but not all animation is anime. The same way all whisky is alcohol, but you wouldn’t hand someone a Johnnie Walker and call it beer. Accurate at the molecular level, completely useless as a description.

If you’ve spent any time in anime communities, you’ve probably seen people throw around phrases like “this is a Winter 2025 anime” or “it’s a split-cour” and just nodded along, hoping it would make sense eventually. It does, once someone actually explains it properly. The system Japan uses to broadcast anime is genuinely different from how Western TV works, and understanding it makes the whole experience of following anime a lot less confusing.

The four seasons

The Japanese broadcasting calendar divides the year into four quarterly blocks that align with the actual seasons. Winter runs from January through March, Spring covers April through June, Summer goes from July through September, and Fall handles October through December. Every three months, a new wave of anime launches, older ones wrap up, and the cycle starts again. Four times a year, every year, in most cases.

This is completely different from how American television operates. A US network show might air 22 episodes over nine months, take a summer break, come back in the fall, and repeat. Anime usually doesn’t work like that. Each quarterly block is often treated as its own contained event, and studios plan their entire release schedule around hitting those specific windows. Missing the start of a season can mean waiting until the next one, which is why delays in anime production are such a big deal.

What is a cour?

This is the word that confuses most newcomers, and it’s also the most important one to understand. A cour, pronounced “koor,” comes from the Japanese word “kuuru,” which itself was borrowed from the French word “cours,” meaning course. Anime fans started using it in English communities around the mid-2000s, and it stuck. Think of a cour the same way you’d think of a semester at school: a fixed period of time with a set amount of content.

One cour equals roughly 12 to 13 episodes aired weekly over a single three-month broadcast season. That’s why the overwhelming majority of anime series land somewhere around that episode count. It isn’t laziness or budget issues; it’s largely how the broadcasting calendar is structured. A studio typically gets a three-month slot, fills it with weekly episodes, and that’s your cour. Simple enough on its own, but it gets more complicated once you factor in how different shows use multiple cours.

Single cour, double cour, and split cour

A single cour anime is the most common format by far. Twelve or thirteen episodes, one season, done. Shows like Chainsaw Man, Erased, and Tomo-chan Is a Girl all fit neatly into this format, telling a complete story within a single three-month window. The story is designed to wrap up within that time, or at least reach a satisfying stopping point.

For studios adapting manga or light novels, a single cour is also the lowest-risk approach because they release the anime, see how people respond, and then decide whether to greenlight more.

A double cour anime runs for two consecutive seasons without a break, which gives you roughly 24 to 26 episodes. Jujutsu Kaisen Season 1 is a good example, airing continuously from Fall 2020 into Winter 2021 with no interruption. More classic examples include Attack on Titan Season 1, which ran straight through 25 episodes in 2013–2014 without a break. Delicious in Dungeon did the same thing in 2024, running from Winter straight through Spring. In other words, the episodes never stop. One season flows directly into the next with no gap between them.

Split cour is where things get genuinely confusing, and it’s also where most of the arguments in anime communities happen. A split cour anime has roughly 24 to 26 episodes total, but instead of airing them back-to-back, the studio releases the first half, takes a break of about one season (~three months) where something else airs in that slot, and then comes back with the second half.

For example, both Mushoku Tensei: Jobless Reincarnation and Re:Zero − Starting Life in Another World used this format, while more recent shows like 86: Eighty-Six have followed a similar split cour approach. The two halves are technically one production season, one unified story, but the break in the middle makes it look and feel like two separate things. To make matters worse, database sites like MyAnimeList sometimes list them separately, which might confuse people further.

Why does any of this exist?

The honest answer is logistics. Japanese animation studios operate with tight schedules, small teams compared to Western TV productions, and budgets that require careful management. Giving a show a 12-episode slot is a way for broadcasters to test audience reception before committing to a longer run. If the first cour performs well in ratings and merchandise sales, the production committee, which is the group of companies that funded the anime in the first place, can greenlight a second cour or a full second season. If it doesn’t, the studio moves on without having burned through resources on 24 episodes of something nobody watched.

The split cour format exists for a similar reason, except it’s more about managing production quality. Delivering 24 episodes of animation at a consistently high level within six consecutive months is genuinely brutal for animation staff. Giving the studio a three-month break mid-production lets them catch up, refine the second half, and come back stronger rather than rushing episodes that look noticeably worse toward the end. Several of the biggest anime in recent years have used this approach specifically to avoid the kind of animation quality drop that One Punch Man Season 2 became infamous for.

How this differs from the West

American network TV was traditionally built around longer seasons, often 20 or more episodes per year, airing over most of the year with a summer break. That system made sense when television was the only screen in the living room and networks needed to hold audience attention for as long as possible.

Now, anime never operated that way. The cour system means a show airs intensely for three months, builds a concentrated burst of community discussion and fan activity, wraps up, and then leaves people waiting for the next installment. That anticipation between cours, and especially between full seasons, is actually a significant part of how anime fanbases work. The week-to-week discussion during a cour, the theories, the reaction videos, the discourse, is almost as much a part of the experience as the show itself.

Interestingly, streaming services have changed the traditional network TV model. Nowadays, many new series run shorter seasons, more like anime cours, with 6–13 episodes released weekly or all at once. Favorite series like Stranger Things, The Witcher, and House of the Dragon follow this format, giving concentrated story bursts that generate intense fan discussion and anticipation between seasons.

What about streaming?

Netflix and other streaming platforms complicated this further by occasionally dropping entire seasons at once instead of weekly episodes, which changes the viewer experience from the traditional weekly rhythm to binge‑viewing.

Many anime were originally created with broadcast cours in mind, but streaming releases don’t always line up with those seasonal windows; Netflix, in particular, has released titles outside the usual Japanese broadcast schedule.

Crunchyroll and most anime‑specific platforms still follow the simulcast model, releasing episodes weekly as they air in Japan, which preserves the seasonal, week‑to‑week community experience.

The long-running exception

All of the above applies to most anime, but there’s a category that throws the whole system out the window, and that is long-running shonen series, such as Naruto, One Piece, Bleach, and Dragon Ball. They air continuously for years, sometimes decades, filling the gap between manga chapters with what fans call filler, original content that isn’t in the source material.

Curiously, One Piece has been airing since 1999 and is still going. These shows operate on a completely different broadcasting logic, designed to never leave the air long enough for the audience to build the habit of watching something else.

Now, understanding the cour system won’t change what you watch, but it will change how you follow it. Knowing that a single cour anime wraps up in three months, that a split cour is coming back after a break rather than being cancelled, and that a new season of something you love is three months away rather than a year, makes the whole thing feel a lot less random and a lot more like the deliberately structured system it actually is.