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Offline Mode

The Reader supports offline reading for cached content. The Reader automatically detects network connectivity and adjusts the interface. Features requiring server communication are disabled when offline. Core reading functionality remains available for cached content. A Network Status Indicator appears in the Footer when offline.

Offline Detection​

The Reader monitors network connectivity through the isOffline state variable. When offline:

A Network Status Indicator appears in the Footer displaying a message indicating the network is unavailable.

Features requiring internet are automatically disabled (grayed out or hidden).

The Reader continues to function with available offline capabilities.

Feature Availability by Network Status​

Core Reading Features​

FeatureOnlineOfflineNotes
Document Viewing✅✅Content must be cached
Page Navigation✅✅
Page Layout Changes✅✅
Theme Selection✅✅
Zoom Controls✅✅
Table of Contents✅✅
Thumbnails (PDF)✅✅
Reading Progress✅✅

Features Requiring Internet​

FeatureOnlineOfflineReason
Search✅❌Requires server-side text search
Notebook✅❌Syncs annotations with server
Highlights (new)✅❌Requires sync to save
Notes (new)✅❌Requires sync to save
Vito AI✅❌AI processing on server
Listen (TTS)✅❌Uses cloud TTS services
Dictionary✅❌Fetches definitions from server
Translation✅❌Uses translation API
Smart Zoom✅❌Requires article data from server
Social Sharing✅❌Requires internet to share

Disabled Feature Behavior​

When a feature is unavailable due to offline status:

Visual State: The button appears grayed out or with reduced opacity

Interaction: Clicking/tapping the button has no effect

Tooltip: May display a message indicating internet is required

Network Status Indicator​

When offline, a notification bar appears in the Footer:

Location: Top of the Footer component

Appearance: Styled to match the current theme

Animation: Fades in when offline, fades out when connection is restored

Content Caching​

For offline reading to work, content must be available locally:

PDF Documents​

PDF pages are loaded as images from publication.files_urls.

Once loaded, pages may be cached by the browser.

Thumbnails use the same image sources and cache similarly.

EPUB Documents​

EPUB content is loaded through the EPUB spine.

Chapters that have been viewed may be cached.

Navigation within cached chapters works offline.

Audiobooks​

Audio files must be downloaded/cached for offline playback.

The Playlist panel works offline.

Playback controls function offline with cached audio.

Feature Availability by Content Type (Offline)​

FeaturePDFEPUBAudiobook
Content Viewing✅✅✅*
Navigation✅✅✅
Table of Contents✅✅N/A
Thumbnails✅N/AN/A
PlaylistN/AN/A✅
Theme✅✅✅
Zoom/Font✅✅N/A
Page Layout✅✅N/A
Search❌❌N/A
Notebook❌❌N/A
Vito AI❌❌N/A
Listen (TTS)❌❌N/A
info

Audiobook playback requires cached/downloaded audio files

Offline Analytics​

Reading activity is tracked even when the user is offline in the mobile and desktop apps (Fenice). Events such as session starts, page changes, and reading time are stored locally on the device and synchronized automatically when connectivity is restored.

This means tenant analytics reports reflect actual reading behavior regardless of whether the user was online or offline during the session. Timestamps preserve the real moment the reading event occurred, not the sync time.

Key points:

  • Events are queued locally for a configurable period (retention is intended to be tenant-configurable from the admin panel; pending full implementation, a local fallback applies)
  • Sync happens automatically on reconnect (no user action required)
  • Reading time and session data in reports include offline sessions
  • Available on mobile and desktop (Fenice). The web reader requires an active connection for analytics
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