ElectricSQL focuses narrowly on the data synchronization problem between PostgreSQL and client applications. It reads the PostgreSQL WAL to detect changes and propagates them to connected clients through a persistent sync connection. Applications maintain a local data copy that responds instantly to user interactions while changes sync bidirectionally in the background, enabling offline operation and eliminating loading spinners for data that has already been fetched.
Supabase provides a comprehensive backend platform where real-time data is one feature among many. Real-time subscriptions through Supabase Realtime notify connected clients of database changes through WebSocket connections. However, Supabase also includes authentication, file storage, edge functions, vector embeddings, and a REST API layer that together provide a complete backend without server-side code.
The architecture for real-time data differs fundamentally. ElectricSQL replicates data to the client's local storage, enabling queries against local data with zero network latency. Supabase Realtime pushes change notifications to clients that then update their application state, maintaining the traditional client-server boundary where data lives on the server and clients receive updates.
Offline capability is ElectricSQL's defining strength that Supabase does not address. Applications built with ElectricSQL continue functioning without network connectivity because all required data is available locally. Supabase applications require network access for data operations, though caching strategies can provide partial offline experiences.
The scope of backend functionality heavily favors Supabase. Authentication, file storage, edge functions, database management UI, and a generous free tier create a complete backend platform. ElectricSQL only handles data sync, requiring teams to choose and integrate separate solutions for authentication, storage, and serverless functions.
Conflict resolution in collaborative scenarios is handled differently. ElectricSQL provides automatic conflict resolution for concurrent modifications using configurable strategies. Supabase Realtime delivers change events and leaves conflict resolution to application logic, which provides more control but requires more implementation effort.
Scaling characteristics differ based on architecture. ElectricSQL's sync service must track subscription shapes for every connected client, with horizontal scaling needed as connection counts grow. Supabase's server-centric model scales through PostgreSQL's proven capabilities and Supabase's managed infrastructure that handles millions of concurrent connections.
The developer experience is more complete with Supabase. Its dashboard provides visual database management, user administration, storage browsing, and log viewing. ElectricSQL is a library that integrates into existing applications, requiring developers to use standard PostgreSQL tooling for database management.