Frequently Asked Questions

AudioBookSync is a smart audiobook player for iPhone and iPad featuring OCR-based text search and an integrated EPUB reader with audio synchronization. Seamlessly switch between reading and listening — the app keeps your book and audiobook automatically in sync. It also supports CarPlay and offers a home screen widget.

AudioBookSync runs on iPhone and iPad with iOS 18 or later.

Yes — the free version includes the full player, the e-book reader, the OCR scanner, CarPlay and the home-screen widget. The free version keeps one audiobook active at a time; you can switch between books for free at any time. The one-time in-app purchase «AudioBookSync Pro» removes this limit. There is no subscription.

Pro is a one-time purchase that unlocks four convenience features: unlimited simultaneously usable audiobooks, automatic listening- and reading-progress sync between iPhone and iPad via your private iCloud Drive, a shared transcription index so books don't need to be indexed on every device separately, and the Apple Watch companion app for offline listening on your wrist. CarPlay, the widget and every playback feature remain part of the free version.

No. All processing (OCR, indexing, sync) happens locally on your device. The Pro multi-device sync uses your private iCloud Drive — the data never leaves your Apple account. Your books stay private.

M4B (with chapter markers) and MP3 (single files or folders with multiple files).

Place your audiobook files in the AudioBookSync folder in iCloud Drive. The app detects and imports them automatically.

Make sure the files are in the correct format (M4B or MP3) and located in the AudioBookSync folder in iCloud Drive. Files must be fully downloaded.

No. AudioBookSync only supports DRM-free files.

The app indexes the audio content of your audiobook. When you scan a book page, the recognized text is matched against the index to find the corresponding spot.

Indexing transcribes the entire audiobook locally on your device. Depending on length, this can take several minutes. Progress is shown in the app.

Ensure good lighting and hold the camera steady. Printed text works better than handwriting. You can also use a photo from your gallery.

Yes — for German, English, French and Spanish. Each book has its own language that drives transcription and text recognition. If an e-book is linked, the app picks up its language automatically; otherwise you set it in the library via the context menu under 'Book language'. Important: the language has to be correct before you index the book — changing it afterwards deletes the index and rebuilds it.

The camera text search and the jumps between text and audio need the audiobook's transcription index. While it is missing or incomplete, the app points that out before you open the scanner and offers to start indexing immediately. Indexing runs locally in the background; depending on the length of the book it takes minutes to hours.

EPUB 2 and EPUB 3. DRM-protected EPUBs are not supported.

Open a book that has both an audiobook and an EPUB. In the reader, you'll find the 'Listen here' button to jump directly to the current position in the audiobook. During playback, the current paragraph is automatically highlighted in the reader.

Sync accuracy depends on the quality of the audio transcription. Make sure the audiobook is fully indexed. Without a transcription index, the app uses a chapter-based fallback that is less precise.

Yes. Your position in the e-book is synced as a listening position. Read on your iPad in the evening and CarPlay starts at that passage the next morning — with no prompt on the screen. This requires an indexed audiobook, since only then can the passage be matched reliably. The app never jumps back more than ten minutes.

Yes. The Watch app is a Pro feature. Once Pro is unlocked, you can listen to an audiobook offline on an Apple Watch running watchOS 10 or later.

Open the audiobook in the iPhone player and tap «Send to Watch» in the toolbar. Choose how much to send starting from your current position: +1 hour, +2 hours, +3 hours, or until the end of the book. The app slices that range, encodes it as M4A at ~64 kbps mono and transfers it together with the cover to your Watch via WatchConnectivity.

Yes, without constant background traffic. When you open the player or reader on the iPhone, it asks the Watch for its current position — and offers a «Continue from here?» dialog if the Watch is newer. Pressing Play on the Watch asks the iPhone the other way around and auto-adopts if the iPhone is more recent.

At 64 kbps mono, expect roughly 30 MB per hour of audiobook. A 3-hour slice is about 85 MB. For uploads larger than 500 MB the app asks for confirmation. Only one slice lives on the Watch at a time — a new one replaces the old one automatically.

Swipe up one page in the Watch player to the Now Playing view and turn the Digital Crown there — that changes the volume of your AirPods or Bluetooth headset. The Crown on the player page only controls the in-app level and can just make playback quieter.

The app itself is small. Storage requirements depend on your audiobooks. Index data takes up about 5–10% of the audio file size.

Yes, once audiobooks and EPUBs are downloaded, everything works offline — including OCR and sync.

Yes, AudioBookSync is optimized for both iPhone and iPad.