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kthoom is a comic book / ebook reader that runs in the browser using modern client-side open web technologies such as JavaScript, HTML5, the File System Access API, Web Workers, Typed Arrays, and more. It can open files and directories from your local file system, the network, or Google Drive.

It is built using pure JavaScript with no external dependencies and can run out of the box (no building, compiling, packing) straight from the browser. Try it here:


You can also specify a comic book to load via the ?bookUri parameter. Some examples:

Or a comic book reading list via the ?readingListUri parameter.


File Support

  • .cbz (zip)
  • .cbr (rar)
  • .cbt (tar)
  • .epub (primitive support, a work-in-progress, see issue #16)

Keyboard Shortcuts

  • O / D / U: Open books by choosing files/directories from computer or by URL.
  • Right/Left: Next/Previous page of book.
  • Shift + Right/Left: Last/First page of book.
  • [ / ]: Prev / Next book
  • H/W: Scale to height/width
  • B: Best Fit mode
  • R/L: Rotate right/left
  • 1/2: Show 1 or 2 pages side-by-side in the viewer.
  • 3: Long Strip viewer.
  • F: Toggle fullscreen.
  • P: Hide metadata viewer and reading stack panel buttons.
  • S: Toggle the Reading Stack tray open.
  • T: Toggle the Metadata Tag Viewer tray open.
  • ?: Bring up Help screen

You can tell kthoom to open as many books as you like in the Choose Files dialog (shift-select all the books you want to open). Then navigate between books using the square bracket keys or use the Reading Stack tray.

Binary File Support

NOTE: kthoom loads in local compressed files and decompresses them in the browser, which means that kthoom has an implementation of unzip, unrar and untar in JavaScript. This code lives in its own library: BitJS, a more general purpose library to deal with binary file data in native JavaScript. Kthoom keeps an up-to-date version of bitjs in its repository.

JSON Reading Lists

kthoom supports loading lists of comic book files at once. Think audio playlists but for comic books! See JSON Reading Lists for more.

URL parameters

  • alwaysOptimizedForStreaming=true: Tells kthoom to render pages immediately as they are de-compressed (this might not work for all comic books as some are not compressed in the order of reading)
  • bookUri=<url>: Tells kthoom to open the given book (cbz/cbr file).
  • doNotPromptOnClose=true: Tells kthoom not to ask the user if they are sure they want to close.
  • readingListUri=<url>: Tells kthoom to load the given JSON Reading List (jrl) file and open the first file in that list.


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