Readest vs KOReader: cross-platform reading or e-ink control?
Readest and KOReader share more history and users than a typical pair of competing apps. Readest's founders previously contributed to KOReader, and Readest supports both the official KOReader progress-sync protocol and a deeper KOReader plugin. The useful question is therefore not “which project should win?” It is which reader belongs on which device.
KOReader is built primarily for dedicated e-ink hardware. It runs directly on supported Kindle, Kobo, PocketBook, reMarkable, Cervantes, Android, and Linux devices and exposes unusually deep control over screens, documents, and hardware buttons. Readest is built to keep one modern library and interface consistent across iOS, Android, Windows, macOS, Linux, and the web. Their overlap is real, but so is the opportunity to use them together.
Last verified: August 28, 2026, against Readest 0.12.1 and KOReader's official 2026 documentation and repository.
Readest vs KOReader feature comparison
| Capability | Readest | KOReader |
|---|---|---|
| Primary focus | Cross-platform library and deep reading | Dedicated e-ink and document viewing |
| Kindle installation | Not on stock Kindle OS; can sync through KOReader | Yes, on supported Kindle models |
| Kobo installation | Not on stock Kobo OS; can sync through KOReader | Yes, on supported Kobo models |
| PocketBook and reMarkable | Sync-oriented, not a native stock app | Native packages for supported devices |
| Android | Native app, including Android e-ink devices | Native app |
| iPhone and iPad | Native app | No |
| Windows | Native app | No standard Windows release |
| macOS | Native app | Emulator/developer route, not a standard app |
| Linux | Native desktop app | Native app |
| Web reader | Yes | No |
| Reflowable formats | EPUB, MOBI/AZW3, FB2, TXT, Markdown | EPUB, FB2, MOBI, DOC, RTF, HTML, CHM, TXT and more |
| Fixed-page formats | PDF, CBZ/ZIP, fixed-layout EPUB | PDF, DjVu, CBT, CBZ and more |
| Scanned PDF/DjVu reflow | No general OCR/reflow pipeline | K2pdfopt-based document reflow |
| E-ink optimization | Contrast, refresh-aware mode, hardware buttons | Core design: no-animation UI, contrast, refresh, dithering, page controls |
| Typography | Fonts, themes, margins, columns, custom CSS, vertical text | Extensive fonts, margins, spacing, styles, hyphenation, rendering overrides |
| Annotations | Highlights, underlines, notes, excerpts, export | Highlights, notes, bookmarks, export |
| Text to speech | Built in across platforms with offline/cloud options | Available on supported builds/devices; less uniform across targets |
| Translation and lookup | Multiple translators, dictionaries, Wikipedia, Word Lens | Dictionaries, Wikipedia, Google Translate and plugins |
| OPDS and calibre | OPDS, calibre/calibre-web, OPDS-PSE | OPDS, calibre metadata and wireless integration |
| Progress sync | Readest Cloud, storage providers, official KOSync | Official KOSync protocol and server |
| Full library sync between the two | Readest KOReader plugin syncs files and reading data | Same plugin runs inside KOReader |
| Parallel reading | Two books side by side, optional synced scrolling | No equivalent first-class split reader |
| Plugin system | Selected integrations; project extensions | Broad Lua plugin and user-patch ecosystem |
| License | AGPL-3.0 | AGPL-3.0 |
| Price | Free; optional paid cloud plans | Free; donation-supported |
Where KOReader is the better choice
Dedicated e-ink device support
KOReader's clearest advantage is that it runs where Readest does not: directly on many Kindle, Kobo, PocketBook, reMarkable, and Cervantes readers. Its interface avoids animation, uses paginated menus, and is designed around slow-refresh grayscale screens and physical keys. Controls for refresh behavior, ghosting, contrast, front lights, page geometry, gestures, and device-specific quirks are not a secondary compatibility layer; they are central to the project.
Readest works well on Android-based e-ink tablets and includes e-ink display options, but that does not make it a native replacement on every dedicated reader. If your primary device is a jailbroken Kindle or a Kobo and you want maximum control without changing hardware, KOReader is the obvious starting point.
PDFs, DjVu, and scanned documents
KOReader supports more document formats and has a mature toolkit for fixed-page material. Its built-in K2pdfopt integration can reflow scanned PDF and DjVu documents, while cropping, contrast, zoom, column navigation, and page fitting can rescue files designed for paper. Researchers who read old scans or technical PDFs on small e-ink screens will find controls that Readest does not attempt to match.
Readest's PDF experience includes text selection, highlighting, lookup, themes, contrast, zoom, and mobile performance work, but it does not claim KOReader's scanned-document reflow depth. For an image-only academic archive, that difference can decide the choice by itself.
Fine-grained automation and plugins
KOReader's Lua plugins and user patches expose behavior that would be too specialized for most reader settings screens. Power users can connect services, remap gestures, automate sleep covers and front lights, alter status bars, or patch the interface. This can require more experimentation, but it rewards people who want the reader to conform to one exact device and routine.
Where Readest is the better choice
A first-party app beyond e-ink
Readest runs natively on iPhone, iPad, Android, Windows, macOS, and Linux, and it has a full browser reader. A person can import a book from an iPhone share sheet, annotate it on an iPad, listen through CarPlay, and continue in a desktop window without changing applications or inventing a file-transfer workflow. The visual model, settings, notebook, and library remain recognizable across those platforms.
KOReader has an Android app and Linux build, but it intentionally carries an e-ink-oriented interface. It does not offer a normal iOS or web client. On a modern phone or laptop, Readest generally feels more like a native consumer app; on an e-ink reader, KOReader's specialized interface is often the point.
Library-wide sync and modern storage choices
The official KOReader Sync Server synchronizes progress. Readest understands that protocol, so the two apps can keep a matching file's position in step. Readest also provides a deeper path: its KOReader plugin can browse a Readest library and transfer book files, bookmarks, highlights, notes, progress, and reading statistics. Manual push/pull controls and sync diagnostics make the boundary visible.
Within Readest itself, readers can synchronize additional categories such as settings, custom fonts, dictionaries, backgrounds, OPDS catalogs, and credentials. Depending on plan and platform, storage can use Readest Cloud, iCloud, Google Drive, OneDrive, WebDAV, or S3-compatible services. The sync documentation explains which path sends which data.
Parallel Read, listening, and language study
Readest can open two books at once, place them side by side, and optionally synchronize scrolling. That is useful for a translation beside its original, a commentary beside a primary text, or two editions being checked line by line. Its TTS can highlight by word or sentence, download voices per book, and continue with mobile media controls. Translation spans a selected passage, a page, or a whole book, while Word Lens places short hints above unfamiliar words.
KOReader includes strong dictionaries, Wikipedia, Google Translate integration, and device-dependent TTS options. Readest's advantage is not the existence of lookup but the integration of these tools into the same cross-platform study workflow.
The best answer may be Readest and KOReader together
For owners of a Kindle, Kobo, or PocketBook, the combined workflow is unusually coherent:
- Install KOReader on the supported e-ink device.
- In Readest and KOReader, configure the official KOSync server with binary/file-content matching for progress-only sync.
- If books and annotations also need to move, install the Readest plugin in KOReader and sign in to the same Readest account.
- Use Readest library inside the plugin to download a cloud book to the e-ink device.
- Read on KOReader for its screen and hardware controls.
- Continue in Readest on a phone or computer with the synchronized position and, when using the plugin path, annotations and files.
The two sync methods solve different problems. Official KOSync is deliberately small and interoperable: it tracks progress. The Readest plugin is broader and account-based. The docs recommend choosing the path that matches the data you need rather than turning on everything without understanding it.
Which should you choose?
Choose KOReader when a supported dedicated e-ink device is the center of your reading, especially for PDFs, DjVu scans, unusual formats, precise refresh control, or plugin-driven customization. It is one of the most capable document viewers available for constrained reading hardware.
Choose Readest when reading is distributed across an iPhone or iPad, Android, desktop systems, and the web; when a synchronized visual library matters; or when Parallel Read, consistent TTS, translation, and annotation workflows are central.
Choose both when you love dedicated e-ink hardware but do not want it to become an island. Readest's explicit KOReader compatibility exists for exactly that audience, and neither project needs to pretend the other's strongest platform does not exist.
Sources and verification
KOReader claims were checked against the official KOReader project site, user guide, and source repository, whose feature list documents supported devices, formats, K2pdfopt reflow, calibre and OPDS integration, dictionaries, translation, and e-ink optimization. Readest claims were checked against the Readest docs, especially Sync with KOReader, and the Readest 0.12.1 release.
Frequently asked questions
- Is Readest a replacement for KOReader?
- Not for every reader. Readest is designed for a consistent experience across phones, tablets, computers, and the web. KOReader remains the stronger choice for direct installation on many dedicated e-ink devices and for advanced PDF and display tuning.
- Can Readest sync with KOReader?
- Yes. Readest supports the official KOReader progress-sync protocol, and a Readest KOReader plugin can sync books, progress, bookmarks, highlights, and notes through a Readest account.
- Which app supports more ebook formats, Readest or KOReader?
- KOReader supports more specialist and document formats, including DjVu, DOC, RTF, HTML, CHM, CBT, and scanned-document reflow. Readest covers the common reading formats EPUB, PDF, MOBI, AZW3, FB2, CBZ, TXT, and Markdown.
- Are Readest and KOReader free?
- Both readers are free and open source. Readest has optional paid cloud plans; KOReader is volunteer-developed and accepts donations.