PDF, CBZ, CBR, CB7 and CBT. No accounts, no uploading a single file to any server, no ads. Pick a file and start reading instantly.
Koma processes everything inside your browser. Nothing you read, not a single file, ever leaves your device.
Your files are stored in the browser's local storage (IndexedDB). No backend, no accounts, no tracking — no one else ever sees what you read.
With no uploads or downloads in the way, page turns are instant. Built to run smoothly even on low-end Android devices.
Pick a file and read. Close whenever you want: Koma remembers the exact page, zoom, and mode you left off in.
All of them share the exact same reading experience.
CBA (the ACE format) is the one exception: it's a proprietary format with no viable browser-side decoder anywhere, so Koma tells you clearly instead of failing silently. Convert it to CBZ to read it here.
Every detail is designed for comfortable reading, not to look like a file viewer.
Page, zoom, direction and bookmarks are saved per title, automatically.
Right-to-left reading with spread detection, so a two-page spread never gets cut in half.
Single page on mobile, optional double page on tablet and desktop — it adjusts to your screen.
Favorites, history, search, and an automatic cover for every file you add.
Fit to width, height, or screen, rotate the page, and control zoom without losing smoothness.
Pages are loaded and released on demand, even in files with thousands of pages, without choking your device.
PDF, CBZ, CBR, CB7 or CBT from your device.
No waiting, no uploading — it opens straight in your browser.
Next time, Koma will be waiting exactly where you left off.
No, never. All processing happens in your browser and your files are stored locally on your device (IndexedDB). Koma has no backend.
Yes — after the first time you open the app with a connection (to download the reading libraries), your browser caches them and Koma works offline from then on.
ACE is a proprietary, essentially abandoned compression format — there's no actively maintained, working decoder for it anywhere in the browser. Convert the file to CBZ and it'll read just fine.
No. Koma is a web app — it opens straight in your browser. On Android you can also "Add to Home Screen" so it feels like a native app.
Only the copy Koma kept for reading gets deleted. Your original file, if it exists elsewhere on your device, is never touched.
Nothing to install, nothing to configure.
Open Koma →