OpenViewer vs ctLibrary
Price, ratings, monetisation and update history for both apps, side by side β with what reviewers say about each.
OpenViewer
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OpenViewer is a lightweight viewer for all standard document formats. [Supported formats] PDF Β· HWP Β· DOCX Β· XLSX Β· PPTX Β· EPUB Β· TXT Β· Images [Key features] β’ Fast launch β’ Dark mode β’ Recent files + favorites β’ 100% on-device processing β’ Native HWP support for Korean documents [Why OpenViewer?] - No in-app purchases - No account required - Ad-supported (no ads inside viewer) - English, Korean, Japanese UI Contact: wowpia0127@gmail.com
ctLibrary
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ctLibrary is a free offline-first document and notes library. Keep PDFs, Word, Excel, PowerPoint, images, text files, and your own typed notes organized in one place β on your device, and optionally synced across your Apple devices through your own iCloud account. ORGANIZE - Folders contain Categories. Categories contain documents and notes together. - Personal folder with Important Documents and Personal Notes categories, ready on first launch. Create your own folders and categories anytime. IMPORT DOCUMENTS - Import PDFs, Word, Excel, PowerPoint, images, text, CSV, RTF, and Markdown. - Share into ctLibrary from Mail, Files, Safari, cloud-drive apps, and more. - Manual import from the Files picker also supported. READ, SEARCH, SHARE - Open PDFs directly in the app with pinch-to-zoom and pagination. - Preview images, text, and CSV files in-app. - Best-effort preview of Office files; fall back to Open With for full editing. - Fast offline search across document titles, descriptions, file names, and note text. - Favorites and Recent Items for one-tap access. NOTES - Type quick notes alongside your imported documents. - Notes search by title and body content. - Combined view shows documents and notes together inside each category. SYNC ACROSS YOUR APPLE DEVICES (OPTIONAL) - Turn on iCloud Sync in Settings to keep your library in sync between your iPhone and iPad through your own iCloud account. - Data stays in your iCloud account; Cozzitech operates no sync server and never sees it. - Sync is off by default β your library can stay 100% on-device if you prefer. OFFLINE-FIRST PRIVACY - Everything stays on your device (or in your own iCloud, if you turn sync on). We never see your documents or notes. - No analytics, no tracking, no advertising. - Optional App Lock with biometric unlock and recovery code. - Optional one-time email verification unlocks unlimited folders, categories, documents, notes, and outbound sharing. ctLibrary is built for people who want a reliable local reference library β emergency-management binders, work procedures, household paperwork, training materials, or anything you want at hand without depending on a third-party cloud.
Screenshots
Verdict
The clearest difference is ads: ctLibrary at none against OpenViewer's shown. ctLibrary also leads on update cadence (daily vs every 2 months). On price, in-app purchases, device support and iOS requirement there is nothing between them.
Scored on Price Β· Rating Β· Positive reviews Β· Number of ratings Β· Update frequency Β· Ads Β· In-app purchases Β· Monetization Β· Best chart rank Β· Devices Β· Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
OpenViewer ships an update every 2 months, ctLibrary daily. The most recent releases landed on September 15, 2026 and September 19, 2026 respectively.
| Parameter | OpenViewer | ctLibrary |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 2 months | Daily β better |
| Ads | Yes | No β better |
| In-app purchases | No | No |
| Devices | iPhone, iPad, iPod β better | iPhone, iPad |
| Requires iOS | 15.1 β better | 16.4 |
| Further details β not scored | ||
| Size | 41 MB | 43 MB |
| Age rating | 4+ | 4+ |
| Developer | BongJun Park | CozziTech LLC |
In-app purchases
OpenViewer
No in-app purchases
ctLibrary
No in-app purchases









