Read webtoons on your e-reader
Webtoons are built for endless scrolling — one image thousands of pixels tall — which e-readers simply can't display. Tanko slices long strips into proper pages sized for your device, and it does it the smart way: each cut is placed on the calmest row of pixels near the page boundary, so cuts land in the gaps between panels instead of through art or speech bubbles.
Pack your strip images into a CBZ (or ZIP) and drop it below. Strips are detected automatically — anything taller than three times its width gets sliced; normal pages pass through untouched.
How to convert a webtoon to EPUB pages
- Pack the strip images into a ZIP or CBZ. Name the files so they sort in reading order — 001.jpg, 002.jpg and so on; natural sorting also handles 1, 2, 10 correctly. One image per episode or several per episode both work.
- Pick your e-reader profile. The slice height is derived from the panel's aspect ratio: each cut targets a page as tall, relative to the strip's width, as the panel is relative to its own width. Slices are then downscaled to the panel like any other page.
- Leave direction on left to right. Webtoons read top to bottom and the pages should advance left to right. Spread mode has no effect on strips, because the strip check runs before the spread check.
- Drop the archive and download. Anything at least three times taller than it is wide is sliced; anything else is treated as a normal page. The result panel shows the total page count after slicing.
What a webtoon long strip needs to become e-reader pages
A long strip is one image, often 800 pixels wide and 20,000 or more tall. An e-reader can only show it shrunk to a sliver or panned in pieces, and fixed-layout EPUB has no scrolling. So the strip has to be cut into pages that match the device's shape.
Tanko computes a target slice height from the strip width and the profile — for an 800-pixel-wide strip and a 1264x1680 profile that is about 1,063 pixels per page. It then places each cut somewhere between 70% and 130% of that height from the previous cut, preferring the row with the least detail, with a mild penalty for straying from the ideal position.
The final slice keeps whatever remains, which can be shorter than the others; the reader letterboxes it. Slices of different heights are all fitted into the panel bounds with their proportions kept, so nothing is stretched.
How the slicer finds panel gaps
Each row of pixels gets a busyness score: the difference between its brightest and darkest sampled pixel, sampled every third column. A gap between panels is a band of one color, so its score is near zero whatever that color is — white, black, or a colored background all work.
The odd sampling stride is deliberate: screentones and checker patterns repeat at even intervals and could look uniform if sampled in step with them. Within the allowed window the row with the lowest score plus distance penalty wins, so a clean gap 20% off the ideal beats a busy row exactly on it.
Strips with no gaps at all, such as continuous painted backgrounds, still get cut at the calmest row available, which tends to be a quiet area of sky or wall rather than a face or a speech bubble. There is no panel detection beyond this; borders and bubbles are not recognized as objects.
Reading the result on Kindle or Kobo
The output is a normal fixed-layout EPUB, so it goes to a Kindle through Send to Kindle and to a Kobo over USB, exactly like a converted CBZ. Grayscale profiles dither the color art to 16 gray levels; the Colorsoft and Libra Colour profiles keep the color.
Webtoon episodes are long, so a season can produce hundreds of pages from a handful of strips. The status line counts the output pages, and the Send to Kindle limits (200 MB via app or web, 50 MB by email) apply to the finished EPUB, not to the strips you started with.
Read the guide
Frequently asked questions
- Will a cut ever land through a panel or speech bubble?
- The slicer searches a window around each page boundary for the least-detailed row — in a typical webtoon that's the solid background gap between panels. Art-dense strips with no gaps get the nearest calm row instead, which is as good as any fixed cut and usually much better.
- What if my webtoon is many separate tall images?
- That works — each strip in the archive is sliced independently and the pages read in order. Mixed archives (some strips, some normal pages) work too.
- Why did my webtoon come out as one small page?
- The image was less than three times taller than it is wide, so it was not classified as a strip. Short episodes or previews under that ratio are treated as ordinary pages and scaled to fit the panel; there is no manual override for the threshold.
- Can I change how tall each sliced page is?
- Not directly. Slice height follows the device profile's aspect ratio so each page fills the screen; the only lever is choosing a different profile, which changes the ratio slightly (1072x1448 is a little taller than 1264x1680).
- Do horizontal strips or 4-koma get sliced too?
- No. Slicing is vertical only and triggers on the height-to-width ratio; a wide horizontal strip is treated as a landscape page and follows the spread setting instead. Four-panel manga on standard portrait pages passes through unchanged.
- Do my files get uploaded anywhere?
- No. Conversion runs entirely in your browser — the file never leaves your device. That's also why there are no size limits or queues.
- Is this really free?
- Yes. Single-file conversion with every device profile and every option is free, with no sign-up and no watermarks.