Open Source Ereader
An ebook collection is built one purchase at a time over years, which makes it unsettling how easily a title can vanish: when the store and the reading app belong to the same company, a revoked license or a discontinued app can pull books you paid for off a device you own. Open source readers cut that link. They treat your books as ordinary files you keep and back up yourself, open formats without asking a vendor for permission, and several can run as a library server on hardware you control. Some are single-device reading apps and others manage or serve a whole collection, so the right pick depends on how big your library is and where you want it to live.
KOReader
Document viewer for e-ink readers with broad format support and device-specific installs
calibre
E-book manager for viewing, converting, editing, cataloging, and sending books to reader devices
Readest
Open-source ebook reader for desktop, mobile, and web with notes, TTS, and cross-platform sync
Calibre-Web
Web app for browsing, reading, and downloading eBooks from a Calibre database
Kavita
Self-hosted reading server for comics, manga, EPUB, and PDF with built-in readers and OPDS
Foliate
E-book reader for Linux with EPUB, MOBI, AZW3, FB2, and comic archive support
Calibre-Web Automated
Self-hosted digital library software that automates eBook ingest, conversion, and organization
Thorium Reader
Cross-platform EPUB reading app with OPDS import, layout controls, and accessibility support
Vivliostyle
Open source CSS typesetting engine for HTML, EPUB, and web publications
Our picks
For most readers the choice comes down to where your books live and what device you read on.
Best for e-ink devices: KOReader KOReader is purpose-built for e-paper, running on Kindle, Kobo, PocketBook, and reMarkable with an animation-free interface. It reads both fixed-page formats like PDF and CBZ and reflowable ones like EPUB, and can reflow scanned PDFs to fit a small screen. Calibre integration and OPDS browsing let it pull from a library you host.
Best for managing a whole library: calibre calibre is the workhorse for organizing a collection on your own machine. It views, converts, edits, and catalogs books across all the major formats, fetches metadata from the internet, and moves titles on and off reader devices. Everything lives in a local library rather than a hosted account, so the collection stays yours.
Best for comics and manga: Kavita Kavita is a self-hosted server built around comics, manga, and webtoons, though it also serves EPUB and PDF. It offers single-page, double-page, and webtoon reading modes, rich metadata and search, and an OPDS feed for third-party apps. Role-based accounts let you share one collection with family or friends.
Best for reading across every device: Readest Readest runs on macOS, Windows, Linux, Android, iOS, and the web, and syncs your books, reading progress, notes, and bookmarks across all of them. It adds text-to-speech, dictionary and translation lookup, and can sync progress with KOReader devices. It is a good fit when you switch between devices constantly.
What separates one open source ereader from another
Formats decide almost everything, and EPUB support alone is not the whole story. If you only read novels, most readers here are fine, but scanned PDFs, comics, and manga are a different workload. KOReader handles fixed-page formats like PDF and CBZ alongside reflowable EPUB, and can even reflow scanned PDFs so the text fits an e-ink screen. Kavita is built specifically around comics, manga, and webtoons, with reading modes tuned to each. If you read mainly on Linux, Foliate covers EPUB, Kindle, and comic formats in a clean native app. Test your messiest files, not a tidy sample.
Then decide where your library should live. A single-device reader keeps things simple, but a large collection is easier to manage centrally. calibre runs a full local library on your own machine, converting between formats and fetching metadata without any account. Calibre-Web and Calibre-Web Automated put that same library in a browser and can send books to your devices, while Kavita runs as a self-hosted server you share with family. If you want the same book, position, and notes on a laptop, phone, and the web at once, Readest syncs across every platform it runs on.
Finally, weigh annotations and access. Highlights and notes are worth years of reading, so favor a reader that stores them in a portable form. Foliate keeps annotations in plain JSON that is easy to export, and Readest can sync progress with KOReader devices. If accessibility matters, Thorium Reader works with the NVDA, JAWS, and Narrator screen readers and ships in many languages. Whatever you choose, confirm your books, covers, and notes stay readable outside the app before you commit a large library.
Related categories
Frequently asked questions
Can open source ereaders open books I bought from a store?+
Often, but not always. Books sold without DRM, or ones you have legally removed restrictions from, open like any other file. Titles locked to a vendor's account are a different matter, since open source readers generally cannot act as an official client for a protected store. If most of your library is tied to one retailer, check whether it offers DRM-free downloads before switching, and expect to keep that vendor's app for the rest.
What formats matter beyond EPUB?+
It depends on what you read. Novels are almost always EPUB, but manuals and papers arrive as PDF, and comics and manga come as CBZ or CBR archives. KOReader and Kavita both handle those archive formats with reading modes suited to them, and KOReader can reflow a scanned PDF so it fits a small screen. A strong EPUB reader is not automatically a good PDF or comic reader, so match the tool to your actual files.
Can I read on a Kindle, Kobo, or other e-ink device?+
Yes. KOReader is built for e-ink and installs on Kindle, Kobo, PocketBook, and reMarkable hardware, with an animation-free interface tuned for e-paper refresh. It reads both fixed-page and reflowable formats and browses OPDS catalogs, so a self-hosted library can feed it directly. On e-ink, test page turns and refresh behavior first, since a reader that feels fine on a phone can lag noticeably on e-paper.
How do I read one library across several devices?+
There are two routes. A library server such as Kavita or Calibre-Web keeps the books in one place and lets each device read over the browser or an OPDS app, so nothing is duplicated. Alternatively, Readest syncs the books themselves along with your progress, notes, and bookmarks across desktop, mobile, and web. The server route centralizes storage; the sync route keeps a copy on each device for offline reading.
Will my highlights and notes be portable?+
This varies more than any other feature. Some readers lock annotations inside an internal database; others keep them in files you can export. Foliate stores highlights and bookmarks as plain JSON, which is easy to back up or move. Before you invest years of reading in one app, make a highlight and a note, then confirm you can get them out in a documented format rather than only inside the app.
Is there good screen reader and accessibility support?+
Some readers treat this as a priority. Thorium Reader is tested with the NVDA, JAWS, and Narrator screen readers and is localized in many languages, which makes it a strong starting point for accessible reading on the desktop. Readest also supports VoiceOver, TalkBack, NVDA, and Orca across its platforms. If accessibility is central to how you read, test the specific reader with your own screen reader before committing.
What is the difference between a reading app and a library server?+
A reading app opens files on one device and shows them to you; a library server stores and organizes the whole collection and serves it to many devices. calibre manages a local library on your machine, Calibre-Web and Kavita expose a library over the web, and readers like Readest, Foliate, or Thorium Reader are the apps you actually read in. Many people run a server for storage and a separate app on each device.