Complete removal of Firefox Sync - Eliminated cross-device synchronization complexity
IndexedDB + localStorage hybrid system - Unlimited local storage capacity (GBs scale vs previous _50MB limit)
Manual export/import for data portability - Transfer data between devices via JSON files instead of sync
Enhanced performance - Fast local queries, memory-efficient pagination, no sync overhead
Bulletproof reliability - Core functionality (getVideo/setVideo) never depends on IndexedDB availability

Layer 1: IndexedDB - Complete video/playlists history with full metadata (unlimited capacity)
Layer 2: localStorage - Fast overlay for recent/active content and lightweight config
Merged view reads - Seamless access to complete history with local changes taking priority
Fail-safe migration - Verified batch migration from old storage with comprehensive error handling
Context-aware access - Extension origin owns IndexedDB, content scripts use RPC for privacy

No cross-device sync - All storage is local-only, eliminating sync conflicts and bandwidth usage
Export/import workflow - Manual data portability replaces automatic sync
Local-only architecture - No network dependencies, works completely offline
Simplified complexity - Removed ₁₃₀₀ lines of sync-related code

Unlimited storage scaling - Handle 100,000+ videos without performance degradation
Memory efficiency - Load only current page into memory, not entire dataset
Fast queries - IndexedDB indexes for timestamp, isShorts, and title search
No sync overhead - Eliminated background sync operations and quota limits

What's Changed

Full Changelog: https://github.com/EdinUser/YouTubeLocalHistory/compare/3.1.5...4.0.0