Natural Syntax vs Penguin
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Natural Syntax
This app enhances reading comprehension by subtly styling text to highlight parts of speech, similar to syntax highlighting in programming. It offers a native ePub reader with full text search and a discovery service for public domain books. Users can customize styling and themes for an improved reading experience.
- Syntax highlighting for parts of speech
- Native paginated ePub display
- Full text search
- Public domain book discovery
- Customizable colors and styles
- Multiple themes (Dark, Light, White)
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As programmers read source code we passively absorb some of the meaning via syntax highlighting for the language. NaturalSyntax aims to do the same thing with natural human language, this will improve reading comprehension and understanding by passively absorbing the parts of speech via subtle styling of the text. Features: • Fully native paginated display of syntax highlighted parts of speech for ePub files • Full text book search • ePub parsed on demand for improved experience • Includes discovery service to download thousands of public domain books • Allows customization of colors and styles for each part of speech • Includes Dark, Light and White themes with different default colors • Allows you to turn on or off highlighting of each part of speech • Synchronizes preferences between all your devices • Uses system interface for interacting with your files • Does not collect or store any personal information Limitations: • Can only process English ePub files • Can only search for public domain books when signed into iCloud
Penguin
This app allows you to read your own comic collection in various formats, with on-device translation for Japanese manga. It offers a customizable reading experience and a smart bookshelf, all while prioritizing user privacy and local data processing.
- On-device manga translation for Japanese comics
- Supports various file formats (CBZ, CBR, PDF, etc.)
- SMB and WebDAV network drive support
- OPDS catalog compatibility
- Smart bookshelf with automatic categorization
- Customizable reading gestures and scrolling
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A comic reader for the books you already own. CBZ, CBR, PDF and EPUB open straight from Files, your Mac, or your NAS — no unpacking, no account, no ads, and no internet needed once a book is on the device. Japanese pages you cannot read? Penguin Viewer translates the speech bubbles on your device and paints the English back into the balloon. ■ Manga and novels in one library - Drop in CBZ, CBR, CB7 (7z), ZIP, RAR, PDF or an image folder. TXT, MD and EPUB novels land on the same shelf. - Auto margin cropping fills the screen with books you scanned yourself. ■ A library in your own folders - Make folders like in Finder, nested at any depth, and drag books between them. - New imports land in the open folder, dozens at a time. Move or delete in bulk, or drag books into your own order. - The folder layout and book order follow you over iCloud. Files are not uploaded and use no iCloud storage. ■ Translation that ends on the device - A manga or webtoon bubble is read sentence by sentence, translated, and painted back where the original lettering was. Vertical Japanese is recognized too. - In novels, translate a sentence or page to read beside the original, or look up words. - Translate a book in advance and pages turn with no wait. Nothing is sent anywhere. ■ Read novels your way - Font, size, line spacing, margins and background change in Text and Layout, live. - Jump chapters from the contents. Position and bookmarks carry between devices. ■ Your NAS and server library - Connect over SMB (NAS), WebDAV or OPDS, compatible with Komga and Kavita. - OPDS-PSE streaming resumes at your page without downloading, so a huge library takes no storage. - Reading position syncs over iCloud, and server credentials stay in the device keychain. ■ Read it the way you want - Single Page, Two-Page, or Smart Two-Page picking by screen ratio, plus right-to-left binding. - Webtoons scroll vertically, or run 120Hz auto-scroll through a binge. Pan sideways while zoomed in. - Multi-gigabyte volumes turn without stutter, and pinch zoom works in spreads too. - A night theme blacks out the reader on your schedule, and Mac turns pages from the keyboard. ■ A library that sorts itself - Smart shelves file books as unread, reading or finished, and ComicInfo groups a scattered series. - Set grid columns and cover size, sort by recently opened, search by title, author or series. ■ A record that grows as you read - Reading statistics, streaks and milestones build the habit. - The reading calendar shows how much you read, iOS widgets show today's, and Face ID locks the app, hiding books from widgets and search. ■ Local AI Translation Benchmark - Measure how fast your iPhone, iPad or Mac translates a manga page. Run it from Translation in Settings. - The result is a single PVScore. A bigger number means a faster device. - The results screen is CRT arcade, scanlines and all. Beat your best and NEW RECORD appears. - Save and share the score as a PNG card, device name and chip included. - Enter a nickname (up to 12 characters) to see the worldwide PVScore top 500. ■ Honest pricing - Almost everything is free. The free library holds 30 books, and sharing the app opens 10 more. - The benchmark and leaderboard are free, with unlimited runs. - An unlimited library is one lifetime Pro purchase, not a subscription. No ads anywhere. ■ Privacy by default - Local first: files, translation, statistics and benchmark results stay on the device. - Leaderboard posts send nickname, score, run log and device info (model, chip, RAM, OS), all shown first. - Linking MyAnimeList sends it your title searches and volumes read. - No account, no sign-up, not a single tracking SDK. Open it and read. - Export your library and reading history, and restore it on a new device. ■ Good to know - Penguin Viewer supplies no manga or novels. It reads files you already own. - The interface comes in 17 languages. Requests left in reviews get built quickly. Novel reading came out of one.
Screenshots
Verdict
The clearest difference is rating: Penguin at 4.5 against Natural Syntax's 4.0. Penguin also leads on review sentiment (100% vs 67%) and update cadence (every 3 days vs every 12 months). Natural Syntax's advantage is iOS requirement (12.0 vs 18.0). On price, ratings volume, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Natural Syntax sells 1 one-off in-app purchase and Penguin sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.
Penguin holds the better App Store score, 4.5 against 4.0. Both are backed by a comparable volume of ratings — 2 and 2 respectively. Written reviews point the same way: 67% of Natural Syntax's written reviews are positive against 100% of Penguin's.
Natural Syntax ships an update every 12 months, Penguin every 3 days. The most recent releases landed on October 12, 2026 and October 28, 2026 respectively.
| Parameter | Natural Syntax | Penguin |
|---|---|---|
| Price | Free | Free |
| Rating | 4.0 (2 ratings) | 4.5 (2 ratings) — better |
| Positive reviews | 66.7% of reviews | 100.0% of reviews — better |
| Number of ratings | 2 | 2 |
| Update frequency | Every 12 months | Every 3 days — better |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Monetization | Free with in-app purchases | Free with in-app purchases |
| Devices | iPhone, iPad, iPod | iPhone, iPad, Mac |
| Requires iOS | 12.0 — better | 18.0 |
| Further details — not scored | ||
| Size | 11 MB | 121 MB |
| Age rating | 12+ | 4+ |
| Developer | Jeremy Buchman | HAEDUN KIM |
Customer experience
Natural Syntax
Penguin
In-app purchases
Natural Syntax
- Color Customization$0.99
Penguin
- Pro Lifetime — Buy Once$3.99
Questions
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Is Penguin free?
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