Syncular

Syncular is an open-source, offline-first SQL sync engine licensed under Apache-2.0. It gives every client a real local SQLite database — OPFS in the browser, native SQLite elsewhere — while a single ordered commit log on the server remains the authoritative source of truth. The project publishes TypeScript and Rust cores that implement one written protocol and pass the same conformance suite.

What It Is

Syncular sits in the local-first / offline-first data sync category. Applications read and write against a local SQLite replica; mutations queue in an optimistic outbox and are pushed to the server commit log, which orders, validates, and fans changes back to exactly the clients authorized to see them. The result is instant local reads, conflict-safe writes, and real-time propagation without requiring a live network connection.

Two Cores, One Protocol

The project enforces cross-platform parity through a spec-first approach:

• TypeScript core (@syncular/client): runs in a Web Worker on OPFS via sqlite-wasm, ships at 31.3 KB gzipped, and powers Web and React targets.
• Rust core (syncular-client + syncular-ffi): packaged as a C-ABI native library and consumed by Swift, Kotlin, Flutter, React Native, Tauri, and bare Rust bindings.

Both cores implement SPEC.md and are held identical by golden byte-level vectors and 95 conformance scenarios run against both in CI. The homepage states bootstrap of 100,000 rows takes approximately 30 ms and realtime propagation p95 is 0.2 ms.

Platform and Deployment Coverage

Syncular targets a wide surface area from a single protocol:

• Client platforms: Web (browser OPFS), React, Swift (iOS/macOS), Kotlin (Android/JVM), Flutter/Dart, React Native, Tauri, Rust
• Server runtimes: Bun/Node via Hono, Cloudflare Workers
• Server storage: SQLite, Postgres, Cloudflare D1
• Blob/segment storage: S3-compatible stores and Cloudflare R2

The scaffolder (bun create syncular-app my-app) generates a working project from minimal, web, or tauri templates.

Key Capabilities

• Scope-based authorization: resolveScopes(actor) in the backend gates every read and write; no data escapes its scope.
• Offline outbox: writes queue while disconnected and replay in order on reconnect with idempotent retry.
• Typed SQL / SYQL: one checked query plan generates typed APIs for TypeScript, Swift, Kotlin, Dart, and Rust via the @syncular/typegen CLI.
• CRDT columns: collaborative text per column, byte-identical across both cores, powered by Yjs via @syncular/crdt-yjs.
• Optional E2EE: per-column AES-256-GCM keyrings with authorized local revocation via @syncular/crypto.
• Windowed sync: partial replicas with atomic eviction and a completeness oracle for large datasets.
• Offline FTS5: generated full-text projections maintained inside the local SQLite mirror.
• Testkit: @syncular/testkit provides an in-process server, fault injection, and a virtual clock for integration tests.
• Multi-tab: Web Locks leader election gives N browser tabs one core, one WebSocket, and one OPFS database; followers promote automatically.

Update: v0.15.44

The homepage and docs reference the current published release as v0.15.44. The GitHub repository records a latest release of v0.5.0 (published July 14, 2026), with the repository last pushed August 1, 2026. The project is under active development with a public ROADMAP.md, TODO.md, and a live conformance suite enforcing spec compliance across both cores.