KuroViewer
KuroViewer guide
KuroViewer is an app for reading the books you put there — nothing else. There is very little to learn: add a book, open it, turn the page. This page walks through the few places where people get stuck.
KuroViewer does not distribute books. The only books you can read are the ones you provide. So the first step is telling the app where your books are.
Copy the folder of books onto the device, then add that folder under Settings > Sources. One archive file (zip / cbz / 7z / cb7), one EPUB, one PDF, and "one folder of images" each count as a single book. A folder of images reads straight through as one book even if it is divided into chapters inside. A folder that also contains archives or PDFs, however, is treated as a shelf rather than a book.
You can connect Dropbox, Google Drive, OneDrive, and SMB (a NAS or shared folder). Once connected, only the list of what books exist is copied to the device, and the library is drawn from that. The contents of a book are fetched only when you open it and when reading ahead.
"Connecting" and "signing in" are different things
Attaching a cloud service or NAS is called connecting. It shows your own library to the app, and your credentials never leave the device. Signing in, on the other hand, means a KuroViewer account, and it exists only so you can continue reading across several devices (chapter 10). Either one alone is fine.
Folders are sorted naturally, so "volume 2" comes before "volume 10". Numbers in file names are compared as numbers, so leading zeros (01) and full-width digits (１０) sort the same way.
There are four tabs along the bottom. There will never be more. On a large screen they move from the bottom to a vertical strip on the left.
Recently added books. Books you have finished are shown dimmed.
The bookmarks you placed, plus the books and shelves you marked as favourites. Each bookmark appears with a small image of that page — an excerpt of the text for a text book.
Find a book by walking through folders. It is essentially a file browser, and it does not use the network.
Sources, display defaults, storage, and your account live here. You do not normally need to open it.
Each cover carries a bar showing how far you have read, so you can see your progress without opening the book. Bookmarks appear as marks on the same bar, and the bar flips left to right to match the binding direction.
In a picture book the words are part of the image, which makes zooming the only way to make text bigger. In KuroViewer zooming always works, on every screen. There is no situation where it stops working, and no setting that turns it off.
| What you do | What happens |
|---|---|
| Tap the outer third on the forward side | Goes to the next page. |
| Tap the middle third | Shows or hides the top and bottom bars (title and seek bar). They hide again automatically after a few seconds. |
| Tap the outer third on the other side | Goes back to the previous page. |
| Swipe / flick | Turns pages. In vertical scrolling the motion carries momentum. |
| Pinch in / pinch out | Zooms out and in (1× to 8×). Always available in every display mode. |
| Drag while zoomed | Moves the part you are looking at. |
| Double tap | Switches between fit-to-screen and 1×, centred on the point you tapped. |
| Swipe at the edge while zoomed | Moves to the next (or previous) page at the same zoom level. You do not have to zoom in again. |
| Long-press a page | Opens the display adjustment menu for that page. |
| Turn past the last page | Moves to the next volume. A confirmation bar appears and continues automatically after a few seconds. |
| Volume keys (Android) | Turns pages. Enable it in the settings. |
The left and right thirds swap according to the binding direction: in a right-bound book, tapping the right side goes forward. The top and bottom bars retract on their own as soon as you start zooming.
A display mode you change is remembered for that volume. Once you have chosen for a book yourself, it will not revert to automatic the next time you open it.
Switches between right-bound (Japanese books and manga) and left-bound (Western books). The default is right-bound. Switching it reverses the tap sides, the swipe direction, the order of pages in a spread, and the order in which a scanned spread is split — all at once. Detection looks first at what the EPUB declares, then at whether the file name or path contains Japanese; but once you correct it yourself, it is never detected again for that book.
Scans of paper books sometimes hold two pages in one wide image. In single-page mode these are split down the middle and shown in binding order. The cover is not split, since covers are often wide to begin with. In spread mode nothing is split — the image simply fills the screen. You can turn this off in the settings.
Brightness, contrast, and gamma can be adjusted from inside the viewer as you read. There is also a separate dimming option for reading in the dark. Automatic trimming of the outer margins is available too, though it is off by default.
An EPUB novel is read differently from a picture book. The text is poured into the screen, so the number of pages changes with the size of the screen and the size of the type. That is why "page 45" does not mean anything in a text book.
Ruby (furigana), tate-chu-yoko (upright digits inside vertical text, as in "12年"), and the rule against starting a line with punctuation are all handled. Brackets and dashes take their vertical forms.
Changing the type size or rotating the screen changes where the pages break. Even so, the place you were reading stays on screen, because what is remembered is a position in the text rather than a page number.
Text books have no pinch zoom; the type size setting takes its place. Type settings are held as a global default, but you can also change them for one book only, and that change is remembered for that book.
Searching within a book
Searching for a word inside the book you have open is part of the first release. Full-text search across every book is left for later consideration.
Three things look alike but do different jobs. They are easy to confuse, so it is worth learning them apart.
The automatically recorded "continue from here". One per book, overwritten every time you turn a page. Nothing to operate, and it survives the app being killed. Opening the book starts from where you were, and "read from the beginning" is one tap away.
Positions you place yourself. You can place as many as you like in one book, and they stay until you remove them. Use the bookmark button in the viewer, or long-press the page. The same action again removes it.
A mark on a book or a shelf itself, with no position attached. A bookmark points at a place inside a book; a favourite points at the book (or shelf) as a whole.
The app does not know where your eyes are on the page, so it marks a single point that represents that page: the visible page in single-page mode, the page you started from in a spread, the page occupying the centre in vertical scrolling, and a character near the middle of the visible page in a text book. It is the same as sliding a slip of paper into the middle of a paper page rather than pointing at a line.
Turning past the last page moves to the next volume. A confirmation bar appears and continues automatically after a few seconds; you can also set it to continue with no confirmation at all. The next volume has already been read ahead, so there is no waiting. A book you have read to the end is marked as finished and appears dimmed in the New list.
Whether to use a spread is decided from the aspect ratio of the screen and of the page at that moment, never from the name of the device. A spread is used only when placing two pages side by side does not shrink either of them. As a result a 21:9 phone naturally shows a single page upright and a spread on its side.
No single image ever straddles the fold. In a spread on an opened device, one page goes on each side of the fold and the width of the fold becomes margin. In single-page mode the page sits on one side, clear of the fold.
Going from single page to spread gives you the spread that contains your current page. Going from spread to single page keeps the side you have not read yet. If you were zoomed in, the view returns to fit-to-screen — carrying a zoomed position across would leave you lost.
Once you connect a cloud service, the books you read accumulate on the device. There are two ways they accumulate, and the only difference is whether they disappear on their own.
Fills up automatically as you read. When it reaches its limit, the least recently used items are removed first. If something is removed, it is simply fetched again the next time you read it.
Volumes or shelves you pick to have on hand in advance. These are never removed automatically. Use them for books you must be able to read while travelling, on a plane, or underground.
The limit is set as a share of the free space on the device. The settings screen breaks down what is using how much, and lets you clear it all at once. Reading ahead — fetching volumes you are likely to read while there is room to spare — comes in the next release. Anything fetched that way is "something that may never be read", so it is the first to go when space runs short.
7z alone is fetched in full before the book opens. The format is built differently from zip, and a single page in the middle cannot be pulled out on its own. This never happens silently — you are told "this will be fetched before opening", together with its size. Once fetched, it opens directly from then on.
The title, author, and synopsis are held once per work rather than once per volume; normally the folder holding every volume is the unit of a work. What is retrieved is saved inside that folder as a small file named .folder_info_data_for_kuroviewer.ini. This is the only file KuroViewer ever writes into your library.
View the same library from another device and the same information appears, because the file is right there. Nothing goes through a server, so what you are reading is never sent anywhere. And to avoid overwriting another app's file by mistake, the identifying first line is checked before anything is written.
No account is needed. Every feature works without one. Creating one adds exactly one thing — your reading positions, bookmarks, and favourites carry across devices, and survive changing phones.
Only the small amount of state you created is synced. No text and no images are placed on the server. What travels is encrypted on the device, so we cannot read it. Syncing costs nothing.
When reading positions do not line up
Devices match books by where the book is kept and where the file sits within it. So the same book seen through Dropbox on one device and through a NAS on another is treated as two different books and is not synced.
EPUB and PDF files protected by DRM cannot be opened. There is no feature for removing protection, so this will not change. Archive formats that are not supported, such as rar and tar, show the same message. For what is planned, see the availability marks at the top of this page and the format table on the front page.
Older archive files sometimes store their file names in a character encoding no longer in common use. You can set the encoding per book. Doing so rebuilds the page order and moves your bookmarks along with it.
The binding direction was detected incorrectly. Switch between right-bound and left-bound in the viewer settings. Once corrected, that book is never auto-detected again.
KuroViewer cannot delete or rename books. It is read-only, so there is no path by which a slip could damage your originals. Reorganise on the side where the files live: the device's file app, the cloud service's own screen, or the NAS.
When a book is gone from its location, it leaves the library too. Bookmarks and reading positions, however, are not discarded straight away. Put the book back where it was and the bookmarks come back with it.
If this does not solve it, please get in touch through support.
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