CBZ is a comic book archive: a ZIP of page images, the same idea as CBR but with an open container.
Common Uses
Comic book archives
Manga storage
Digital comics
CBZ Optimization FAQ
What is a CBZ file?
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CBZ (Comic Book ZIP) is a ZIP-based archive format for digital comic books.
What is actually inside a CBZ file?
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A folder of page images in reading order, compressed into one archive with a different extension. There is no text layer and no reflow — a comic page is a picture, and the reader's job is simply to show them in sequence. That makes conversion mostly a question of what happens to the images: page size, compression and whether double-page spreads are split. CBZ is a Comic Book ZIP — the same idea as CBR but built on the open ZIP format instead of RAR.
Why are the pages in my CBZ different sizes?
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Because each page is an independent image and nothing in the format enforces consistency. Scans made in different sessions, at different resolutions, or with double-page spreads left unsplit all end up in the same archive, and the reader simply scales each one to fit as it arrives. A conversion can normalise them to a common width, which is worth doing before sending the file to a small screen.
Can I search the text inside a CBZ?
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Not as it stands. The lettering is part of the artwork — pixels rather than characters — so there is nothing for a search to match and nothing to reflow at a larger font size. Optical character recognition can add a text layer over the pages and make them searchable, but the result is a document about the comic rather than a comic, so it is rarely worth it for reading.
Is the cover image kept when I convert a CBZ?
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It is, provided the book records one as the cover rather than merely having a picture on its first page. That distinction is why a converted book sometimes shows a blank placeholder in a library: the image is still inside the file, but nothing marks it as the cover, so the reader app displays nothing. It is metadata rather than content, and it can be set afterwards without touching the text.
Can a CBZ be reflowed to fit a phone screen?
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Not without converting it. The layout in a CBZ is fixed, so a phone can only scale the whole page down — which is why reading one on a small screen means pinching and panning. Converting to a reflowable format re-derives the reading order and lets the text rewrap at whatever size is comfortable, at the cost of the original page design. CBZ has no text layer, so the pages are not searchable and the text cannot reflow on a small screen.
Is a CBZ really a ZIP archive underneath?
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It is, and renaming a copy and opening it with any archive tool proves it: inside are the structured parts the format is built from, plus the images and fonts they reference. That design is why these files compress well, why a damaged one can sometimes be partly recovered, and why software that is not the original application can read them at all. It is not an invitation to edit the parts by hand — the manifest has to stay consistent. The archive holds one image per page in filename order, with an optional ComicInfo.xml carrying series metadata.
Does it matter that CBZ is over thirty years old?
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Age itself is not the problem — several formats from that era are still perfectly good, precisely because everything has had decades to implement them. What matters is what the era assumed: small files, modest processors, no network, and features nobody needed yet. Where those assumptions still fit, the format is fine. Where they do not, that is the reason to convert.
Who controls the CBZ format?
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Nobody, and that is the point of it. The specification is public, anyone may implement it without asking or paying, and no company can change the terms later — which is why archives, standards bodies and public institutions specify formats like this one for anything that still has to open in twenty years. The trade is not compatibility, which is excellent; it is that there is no vendor to call when some tool implements the spec badly.
Can I convert a whole folder of CBZ files in one go?
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With an account, yes — drop them in together and they are queued as one job rather than handled one at a time, with the same settings applied across the batch and the results returned together. Free conversions run a single file at a time (merge tools take two); a paid plan is what unlocks batch processing and the larger per-file limit, which is what makes converting a whole archive practical.
What happens to my CBZ file after the conversion?
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It is deleted. The upload and the converted result both sit on the server only as long as the job needs them and are then removed automatically; the transfer runs over HTTPS in both directions. Nobody reads the contents, nothing is indexed, and nothing is passed to anyone else. If you would rather not wait for the automatic sweep, closing the job removes the files immediately.
How long does converting a CBZ take?
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Usually seconds. Small files are effectively instant, and the cases that take real time are the ones doing real work: a long recording that has to be re-encoded frame by frame, a scanned document going through character recognition, or a very large batch. Where a conversion only rewraps or repackages the existing data it stays fast no matter how big the file is, because nothing is being decoded.
