# GemReader > GemReader is a free, offline-first study reader for Android. It opens EPUBs, PDFs and interactive workbooks in a single encrypted library, turns the highlights you make into a spaced-repetition flashcard deck, and reads any book aloud — with no account, no subscription and no telemetry. Highlights and notes can be tagged and reviewed across the whole library at once, and a built-in catalog downloads public-domain books from Project Gutenberg, Standard Ebooks and Wolne Lektury. Privacy is built in by default: every book is AES-256 encrypted on import, and PIN-locked secret folders let users hide sensitive reading from the main library. ## About GemReader is built for people who read in order to learn — students, language learners, and anyone working through a textbook. Set texts, lecture PDFs, scanned handouts and interactive workbooks all live in one library, so a course doesn't need four apps. Highlights and typed notes stay anchored where you left them, and can be studied as a built-in spaced-repetition deck without exporting anything; existing Anki decks (`.apkg`/`.txt`) import too. A built-in dictionary answers word lookups without leaving the page, and text-to-speech narration turns any chapter into audio. Every gem — highlight, note, image note or saved workbook answer — can be tagged, and the whole library's gems can be searched and filtered from one list rather than book by book. Books that are out of copyright can be found and downloaded without leaving the app, from Project Gutenberg, Standard Ebooks and Wolne Lektury. The app opens immediately, requires no sign-up, and everything except explicitly requested downloads and catalog browsing works offline. It implements the full EPUB 3.3 specification — CSS3 layouts, custom fonts, JavaScript execution, media overlays, and fixed-layout documents — so books render exactly as their authors intended. The UI is available in 15 languages: English, Spanish, Portuguese, Hindi, Indonesian, French, German, Japanese, Arabic, Chinese, Khmer, Burmese, Amharic, Russian, and Korean. ## Key Features - **EPUB and PDF in one library** — full EPUB 3.3 support (CSS3 layouts, custom fonts, JavaScript, media overlays, fixed layout) alongside PDF rendering with forms, links, pinch-zoom, in-document search and dark mode; MOBI, AZW, AZW3 and CBZ comic archives also supported (ComicInfo metadata and right-to-left manga honoured) - **Highlights & Notes** — six highlight colors with typed notes (Markdown supported) anchored to any highlight, plus notes attached to images; colors can be renamed per book, gems can be tagged, and every highlight and note in the library is browsable in one searchable list - **Free book catalogs** — Project Gutenberg, Standard Ebooks and Wolne Lektury browsable and searchable in-app over OPDS, with any other HTTPS catalog addable by URL; downloads are encrypted on arrival like any other import - **Gem Beam** — hand a whole collection to a nearby phone over a direct Wi-Fi link the two devices set up between themselves: one shows a code, the other scans it, and covers, reading position, highlights, notes and study progress travel with the books. No internet, no account, no cloud; everything is encrypted before it is sent, and an interrupted transfer resumes where it stopped - **Spaced-repetition review** — highlights and notes become a study deck on a dedicated Review page; Anki `.apkg` and `.txt` decks can be imported and drilled in the same app - **Workbook Memory** — every input, textarea, and select in an EPUB 3.3 document is auto-saved and survives app close or crash - **Text-to-speech narration** — listen to any book, attach custom audio per chapter, and control playback from the lock screen - **Built-in dictionary** — word definitions without leaving the page; full-book search and automatic pinyin generation for CJK content - **Beautiful library** — colorful book grid with nested collections, search, and a "continue reading" strip with progress tracking - **AES-256 encryption** — every book encrypted on import; decryption happens in memory only, never written to plaintext storage - **PIN-locked folders** — secret folders protected by a numeric PIN; after 3 wrong guesses the folder self-destructs and keys are wiped - **Screenshot protection** — OS screenshot API blocked inside locked folders; content excluded from the recent apps switcher - **Clipboard auto-wipe** — clipboard cleared automatically when backgrounding from a locked folder - **Gem Lists** — import a `.gemlist` manifest to download an entire reading list into the library in one go - **15 languages** — full UI localisation, works entirely offline ## Pages - [Home](https://www.gemreader.com/): Product overview, the read-mark-review study loop, features, and download links - [Download](https://www.gemreader.com/download): Google Play and direct APK download, installation instructions, and permissions disclosure - [Tour / Screenshots](https://www.gemreader.com/tour): Annotated screenshots of every major screen — library, highlights, flashcard review, dictionary, workbooks, read-aloud, PDFs, and the tablet split view - [Book Checker](https://www.gemreader.com/book-checker): Browser-based checker for EPUB, PDF, MOBI, AZW and AZW3 files — reports whether a file is DRM-locked, whether a PDF has a real text layer or is only scanned images, whether form fields are present, and whether the file will open at all; runs entirely client-side, nothing is uploaded - [Free Tools](https://www.gemreader.com/tools): Index of every in-browser tool below - [EPUB Metadata Editor](https://www.gemreader.com/epub-metadata-editor): Edit an EPUB's title, authors, cover image, language, publisher and description in the browser and download the corrected file; only the package document and cover are rewritten, every other entry is copied byte-for-byte; nothing is uploaded - [EPUB Validator](https://www.gemreader.com/epub-validator): Structural check for an EPUB that will not open — ZIP readability, META-INF/container.xml, package document well-formedness, required metadata, manifest files missing from the archive (including case mismatches), spine integrity, table of contents and unsupported compression; client-side - [EPUB Reading Time](https://www.gemreader.com/epub-reading-time): Word count, CJK character count, paperback-page equivalent and reading time at 150/238/350 words per minute for any EPUB, counted client-side across every spine document - [Kindle DRM Checker](https://www.gemreader.com/kindle-drm-check): Reads the PalmDOC encryption flag in an AZW, AZW3 or MOBI file to report whether Amazon DRM locks it; client-side - [Kindle Highlights to Anki](https://www.gemreader.com/kindle-highlights-to-anki): Converts a Kindle's My Clippings.txt into an Anki-importable deck (tab-separated, one tag per book, also importable by GemReader's Review page) or a Markdown file of quotes grouped by book; merges re-highlighted duplicates, attaches notes to their highlights, skips bookmarks; client-side - [PDF Text Layer Checker](https://www.gemreader.com/pdf-text-layer-check): Reports whether a PDF has selectable text (fonts present) or is scanned images only, and explains OCR as the fix; client-side - [GemList Builder](https://www.gemreader.com/gemlist-builder): Browser-based tool for building a `.gemlist` manifest — a list of book URLs GemReader can import in one go; runs entirely client-side with no upload - [Moon+ Reader Alternative](https://www.gemreader.com/moon-reader-alternative): Honest GemReader vs Moon+ Reader comparison — feature table, what Moon+ still does better (cloud sync, comics/FB2/TXT, customisation depth), what GemReader adds (highlights to flashcards, workbook memory, encrypted library, no ads or Pro tier), and switching FAQ - [ReadEra Alternative](https://www.gemreader.com/readera-alternative): Honest GemReader vs ReadEra comparison — ReadEra wins on document formats (Word, DjVu, FB2, TXT, CHM), reading files in place, Premium Google Drive sync and an existing iOS app; GemReader adds highlights to flashcards, workbook memory, free read-aloud and library-wide highlight list with no paid tier, in-app free catalogs and an encrypted library - [Lithium Alternative](https://www.gemreader.com/lithium-alternative): Honest GemReader vs Lithium comparison — Lithium is a minimal EPUB-only reader with a Pro unlock for Google Drive sync; GemReader adds PDF, MOBI, AZW3 and CBZ in the same library, highlights to flashcards, read-aloud and an encrypted library - [Commonplace Book App](https://www.gemreader.com/commonplace-book-app): Using GemReader as a digital commonplace book — highlights as entries, tags and renamable colours as headings, Markdown notes as commentary, the library-wide gems list as the index, spaced-repetition review, quote cards and Markdown export; limits stated - [Reading Guides (Blog)](https://www.gemreader.com/blog): Articles on Android EPUB reading, study workbooks, privacy, and choosing tools — available in multiple languages. Notable guides: [Best Free EPUB Readers for Android](https://www.gemreader.com/blog/best-free-epub-readers-for-android) (six apps compared by use case), [How to Turn Ebook Highlights into Flashcards on Android](https://www.gemreader.com/blog/how-to-turn-ebook-highlights-into-flashcards-android), [How to Open AZW3 and MOBI Files on Android](https://www.gemreader.com/blog/how-to-open-azw3-mobi-files-on-android), [How to Check if an EPUB Has DRM](https://www.gemreader.com/blog/how-to-check-if-epub-has-drm) - [What's New](https://www.gemreader.com/whats-new): Full version history in plain language — features added per release - [Privacy Policy](https://www.gemreader.com/privacy): Data handling — the app collects no user data and has no telemetry; the website's own hosting analytics and the APK download are disclosed separately - [Terms of Service](https://www.gemreader.com/terms): Usage terms - [Support](https://www.gemreader.com/support): Support page for the app stores — contact address (support@gemreader.com), troubleshooting for DRM-locked books, forgotten folder PINs, libraries missing after a reinstall, read-aloud voices and scanned PDFs, and what to include in a bug report - [Contact](https://www.gemreader.com/contact): Support and feedback ## FAQ ### Is GemReader really free? Yes. Free forever — no ads, no paid tier, no premium gate. There's nothing to unlock and nothing to subscribe to. ### Do I need an account or an internet connection? No. There's no sign-up, and reading, highlighting and reviewing all work with the phone in airplane mode. The app only uses the network when you explicitly ask it to — browsing the built-in book catalog, downloading a book from a Gem List, or opening the in-app browser. It has no analytics, no crash reporting and no ad SDKs, so nothing about your reading is ever sent anywhere. ### Where do the free books come from? Project Gutenberg, Standard Ebooks and Wolne Lektury — three long-standing libraries of books that are out of copyright. Search them from inside the app and a book downloads straight into your library, encrypted on arrival like anything else you import. You can add any other HTTPS catalog you trust. Your device talks to those sites directly: they see the request, we never do, and nothing about you or your library goes with it. ### What files does it read? EPUB and PDF, plus MOBI, AZW, AZW3 and CBZ comic archives. Textbooks, lecture slides, scanned handouts and interactive workbooks all live in the same library. Diagrams, layouts and exercises display the way the author made them, and your workbook answers save automatically. ### Can it turn my highlights into flashcards? Yes. Everything you highlight can be studied as a spaced-repetition deck on the built-in Review page — no exporting, no second app. If you already use Anki, you can import your existing decks (.apkg or .txt) and drill them alongside your own highlights. ### Can it read books out loud? Yes. Text-to-speech narration works on any book, with playback controls on your lock screen. You can also attach your own audio to a chapter — a recorded lecture, for instance — and listen to that instead. ### What phones does it run on? Android 10 or higher — phones and tablets going back to 2019. Install it from Google Play or download the APK directly from this site — it's the same app either way. Phones on Android 7, 8 and 9 keep the last version that supported them, and it goes on working; they simply stop receiving updates. ### What happens to my books if I uninstall? Your books are stored, locked, inside the app — safe from other apps, but they're removed if you uninstall GemReader. Before uninstalling, send your books out with the Share button, or keep your original files somewhere safe. ### Is the Google Play version the same as the direct download? Yes — it's the exact same app, either way. You can install from Play or download the file straight from gemreader.com; you get the same GemReader, from the same signing key. ### Is installing the APK directly safe? Yes — when you trust where it comes from. The download is served over HTTPS from a GitHub Release on the public repo cnohall/gem-reader-releases, and Android verifies the signature before installing, so a file that has been altered will not install. Google Play is still the easier route, because it updates the app for you. ## Recent Updates **v1.34.0 (2026-09-24):** Notes save as you write, with an Undo when you close one, and in landscape a note opens as a tab in the study rail beside the text instead of over it. Back up your library as a plain ZIP of your book files, readable by any other app. Links inside footnotes jump where they point, and .gempack links on gemreader.com open straight in the app. PDF highlights with a note show a note mark. Fixed: PDF form answers lost on a page turn, PDFs going blank or flashing white in dark mode, PDF notes opening on an empty page, and scroll mode skipping chapters. **v1.33.0 (2026-09-21):** Highlight PDFs. Press and hold on a word to start selecting, and the passage is marked in your last-used colour or underlined; a mark takes a note, shows in your gems labelled with its page, and goes into Markdown and Anki exports with that page as its locator. Comics get a page counter, a scrubber and pages unpacked ahead of a turn, and tapping a page turns it or brings the toolbar back. Free books adds Hindi and Arabic shelves from the Digital Library of India. Dark mode can leave a PDF’s colours alone. A GemPack backup can be beamed straight to another phone. Fixed: form answers leaking between workbook chapters, an Undo snackbar that never left, turning pages clipped inside the margin, duplicate app windows in Recents, and glide typing in name fields. **v1.32.0 (2026-09-11):** GemReader reads comics. Import a .cbz the way you would any other book and it opens in the reader a page at a time, with pinch to zoom and the page turns you already use, in numeric order — so an archive whose pages are named 1, 2 and 10 reads in that order rather than 1, 10, 2, which is how most scans are named and how most readers get them wrong. A ComicInfo file fills in the title and author, a book marked as right-to-left manga turns its pages that way, and the controls that need words are left out. Free books carries comics as well as ebooks now: two hand-checked archive.org collections of Golden Age comics in the public domain, in a section of their own. Fixed: the Import button ignoring the first tap after launch on three-button navigation, highlights sitting away from the words in study publications at any text size but the default, and a highlight losing a bite to a link belonging to a different paragraph. **v1.31.0 (2026-09-05):** The library answers gestures now: swipe a book sideways to favourite or delete it, pull the shelf down to refresh, tap the tab you are already on to return to the top, and rate a review card by throwing it left or right. Deleting a book no longer asks first — the book leaves the shelf immediately and Undo stands for seven seconds, with nothing destroyed until it lapses. Haptic feedback becomes one vocabulary of seven cues with a switch to turn it off, waits show the shape of what is coming instead of a spinner over empty ground, and entering a collection or a book feed travels in a direction rather than cutting. On a tablet, single-column lists of text are held to a reading measure. The 2.6 GB chapter-summary model can finally be deleted, from Settings → Advanced. Fixed: immersive reading ending by itself on the next resume, chapter summaries coming back as one word repeated for pages, and a cover lost when a move between a locked and an unlocked folder half-failed. **v1.30.0 (2026-09-04):** Library, Gems and Review moved from icons in the top-right corner to a bar along the bottom of the screen, where a thumb can reach them, with a button of its own for importing a book just above it — and on a tablet, or a wide enough half of a split screen, that bar becomes a rail down the side. The rest of the app’s furniture is rebuilt on Material Design 3: larger text throughout, a ripple from the point you touch, sheets you can drag and fling away, a library header down from seven buttons to one, and sheets held to a readable width on a tablet instead of running the whole way across. The page you read is deliberately untouched. Two more free catalogs to browse — Palace Bookshelf, and Ebooks libres et gratuits for French — and covers saved before GemReader stored them as thumbnails are quietly re-encoded, giving back the space the full publisher artwork was taking. Older releases, back to v0.3.0 (2026-05-29): https://www.gemreader.com/whats-new ## Technical - Platform: Android 10+ (minSdk 29; targets Android 16 / API 36) - Formats: EPUB (full EPUB 3.3 spec support; EPUB 2 compatible), PDF, MOBI, AZW, AZW3, CBZ comic archives - Price: Free, no in-app purchases - Distribution: Google Play (production) and a direct APK published as a GitHub Release on the public repo cnohall/gem-reader-releases, linked from the download page — same binary and signing key either way; APKs from mirrors or aggregators are not official - Encryption: AES-256 GCM at rest; Argon2id-derived keys for PIN folders and the app-lock PIN; keys never leave the device - Offline: reading, annotation and review are fully functional with no internet connection; only Gem List downloads, the in-app browser and the book catalog need one - Book catalog sources: Project Gutenberg, Standard Ebooks and Wolne Lektury by default (OPDS), plus any HTTPS catalog the user adds. Requests go directly from the device to those sites, which see the request the way any website does; no GemReader server sits in between, and no account, identifier or library contents are sent - Permissions: file storage (book import); network (only for transfers the user initiates — Gem List downloads, the in-app browser and browsing or downloading from the book catalog; there is no GemReader server to contact); camera (optional — QR code scanning only, processed locally, never for photos); biometrics (optional — app lock, verified on-device); notifications (optional — read-aloud playback controls); screen-capture detection (so PIN screens and locked collections can block screenshots). Also declared, but never prompted for: wake lock, vibration, network-state, and the foreground-service and boot-completed entries the read-aloud player needs. The Android permission list also shows RECORD_AUDIO, declared by the audio-playback and QR-scanning libraries the app depends on; GemReader contains no recording code. - No accounts, no telemetry, no analytics, no crash reporting, no advertising SDKs ## Full Text - [Complete guide text](https://www.gemreader.com/llms-full.txt): Every reading guide in full, for retrieval and citation - [RSS feed](https://www.gemreader.com/feed.xml): New reading guides as they publish