1
Read-ahead — the next page is already here
Pages around your position are fetched and decompressed in advance. Turning a page never triggers a download or an unzip. When free space allows, the read-ahead window widens on its own.
Your library, everywhere
KuroViewer
Books in the cloud,
as fast as books on your phone.
Cloud books feel slow because of round trips, not file size: opening a volume downloads the whole thing, and the next volume repeats it. KuroViewer prepares the next page — and the next volume — before you turn to it, and lets you pin whole volumes to have them ready in advance. Archives, PDF and EPUB all sit on the same shelf.
Why it opens instantly
Ready before
you turn the page.
Not a trick to make it feel faster. Every place where waiting happens has been removed one at a time: fetching happens while you read, so nothing is left on the page-turn path.
2
No pause between volumes
As you approach the last page, the next volume starts downloading. By the time you turn past the end, it is already there. The faster you read, the more it shows.
3
Pinned downloads — certain, even offline
Pick volumes or whole shelves and download them ahead of time. Unlike the cache they are never evicted, so on a plane, on a train or underground, what you pinned always opens.
4
On-device index — listing needs no network
What you own, and where it lives, is mirrored onto your device, so your shelf opens without a connection. The cache tracks archives and extracted pages separately, capped by a single total.
Read-ahead and page preparation ship in the first release. Cloud and NAS connections, and pinned downloads, arrive in the next one.
Formats
Archives, PDF and EPUB.
One viewer for all of it.
No switching apps by file type. Scans zipped into cbz, technical books as PDF, novels as EPUB, or a plain folder of images — they all sit on the same shelf and read with the same gestures. Archives are never fully extracted to be opened: only the pages you need are pulled out, so a several-hundred-megabyte volume opens without a wait.
Formats
Split between what the first release reads and what comes later. We would rather not imply that something might open when it does not.
- Image folders (JPEG / PNG / GIF / WebP) First release
- zip / cbz First release
- EPUB (reflow, vertical) First release
- PDF First release
- Fixed-layout EPUB Later
- rar / 7z / tar Later
- DRM-protected books Not supported
Where your books live
On-device folders ship first. Cloud storage and SMB are connected once the reading experience is settled — speed machinery is pointless if the reading is not good.
- Folders on this device First release
- Dropbox Next release
- Google Drive Later
- OneDrive Later
- SMB (NAS, shared folders) Later
Why KuroViewer
Reading is the only
job it takes on.
KuroViewer reads the books you already have. It does not distribute them, collect them, or sell them. In exchange, it does not compromise on reading.
No waiting
Readable the moment it opens
Your shelf appears without network access, and a book starts before the full download finishes. Page turns are kept clear of any I/O or decompression.
Everything opens
Your books, as they are
Image folders, zip / cbz archives, EPUB and PDF. Photo books, art books, magazines and scanned doujinshi open in the same viewer as comics — comics are not a special case.
Vertical Japanese
Vertical Japanese novels
Text-first EPUB reflows to your screen and type size, with vertical writing, ruby, tate-chu-yoko and Japanese line-breaking rules. Resize the type and you keep your place.
Any screen
No screen is an exception
Tablets, 21:9 phones and foldables are all standard cases. Instead of enumerating devices, the two-page decision comes from the live measurements of the screen. No single image ever straddles the fold.
Works offline
Offline never breaks it
Reading position and bookmarks are written to disk. Lose signal, or lose the app, and your place is still your place. Downloaded books stay readable.
Read only
Your originals stay untouched
There is no edit, rename or delete. Nothing in the app can damage a file in your cloud. The one thing it ever writes is a small sidecar holding series information.
The reading experience
Handled like
a paper book.
In an image-based book the text is part of the picture, so zooming is the only way to make it bigger. In KuroViewer, pinch zoom always works — on every screen, in every mode. There is no place it stops working and no setting that disables it.
Stay zoomed across pages
If you are following small print, you should not have to zoom again on every page. Scale and position carry over as you turn.
Right-to-left or left-to-right
Switching the binding direction flips tap zones, swipe direction, two-page ordering and the split order of spread scans — all at once. Nothing is left behind.
Spread scans split themselves
A scan holding two pages in one image is split down the middle for single-page view and shown in order. The cover is left alone.
Bookmarks, and where you left off
Your position is recorded on every turn. Bookmarks are unlimited per volume. Covers on the shelf carry a bar showing how far you have read.
It never touches your originals
Your books
stay yours.
KuroViewer is a read-only viewer. Books come from the storage you connected — the app never distributes them, and never fetches them from anywhere else.
Originals are never rewritten
Editing, renaming and deleting are not implemented. The only thing written is the series-information sidecar (.folder_info_data_for_kuroviewer.ini).
DRM is not removed
DRM-protected EPUB and PDF are reported as unsupported and are not opened. There is no facility to strip protection.
Not a downloader
There is no way to fetch books from the web. You can read what is in the storage you connected, and nothing else.
No sharing, no uploading
There is no path that uploads a book or hands it to someone else. What leaves your device is a countable, documented list.
Pricing
Free. Ads only while
the book is closed.
The app is free. One banner sits at the bottom of the list screens. Nothing is shown while you read, and nothing between volumes — that is a specification, not a promise.
- Paying adds no formats and no cache. A feature gap would push a 'free tier limit' axis into the cache design, muddying decisions that exist to serve reading.
- Ads appear only at the bottom of the New, Bookmarks and Search screens. Never while reading, never between volumes, never in settings. No interstitials.
- No account required — everything works without one. Create one and your reading position and bookmarks follow you across devices, at no charge.