RxDB

Overview

RxDB is an embedded NoSQL database for JavaScript applications, built for developers who want client-side data and control over how it is stored and synchronized. Its appeal is the combination of offline operation, reactive queries and broad runtime and storage support; the trade-off is a Free-tier collection cap and paid plans for several storage and performance capabilities.

Key features

RxDB keeps data on the client, so an application can continue operating offline or run entirely without a backend. When synchronization is needed, its Sync Engine works with options ranging from RxServer and GraphQL to Firebase, Supabase, MongoDB, CouchDB, WebRTC, Appwrite, Google Drive and Microsoft OneDrive. That breadth is useful for teams fitting a database into an existing stack, but it also leaves the choice of storage and sync path to the developer.

Observable queries update when stored data changes, suiting interfaces that need current results without manual refreshes. Collections use JSON Schema, with validation and migration support. A password-based encryption plugin protects locally stored documents and works in browsers, React Native and Node.js.

Storage options include LocalStorage, IndexedDB, OPFS, SQLite, Node.js Filesystem, Expo Filesystem, MongoDB and FoundationDB, among others. The distinction matters: LocalStorage is intended for simple browser setups and very small datasets, not large data or heavy writes. RxDB runs in browsers, mobile apps, desktop applications and servers, giving JavaScript teams latitude to choose their deployment environment.

Deployed applications make no requests from users to an RxDB server, and premium plugins contain no tracking code. That is a useful privacy property for applications whose data should remain between client and chosen backend.

Pricing

The Free plan costs nothing, billed forever. It includes RxDB core, replication and realtime sync, default storages, community support through GitHub and Discord, and up to 13 open collections in parallel. The Apache 2.0 license and no-cost entry make it a practical starting point, but projects needing more than 13 simultaneously open collections must look beyond it.

Pro costs $99 a month, billed annually, with unlimited developers. It adds OPFS, IndexedDB, SQLite and Filesystem storage, WebCrypto Encryption and Fulltext Search. This is the step up for teams that need these storage choices or capabilities; the annual billing term is important when comparing it with the forever-free plan.

Pro Plus costs $239 a month, billed annually, also with unlimited developers. It adds Worker and Shared Worker storage, Sharding, Memory-Mapped, optimizers, Fastify/Koa adapters and a Sentry-compatible logger. It is aimed at projects that need those specific additions rather than simply a larger team allowance.

Enterprise has custom pricing and a custom commercial license. It includes a named engineer, architecture review, priority fixes, source-code access and a support SLA with a 24-hour first response, making it the plan for organizations that need that level of support and engagement. RxDB offers no free trial.

Platforms

RxDB supports Android, iOS, Linux, macOS, Windows, web, APIs and self-hosted deployments. Its browser, mobile, desktop and server runtimes make it relevant across a JavaScript application's stack, rather than only as a browser database.

Who it's for

RxDB is a strong fit for JavaScript teams building offline-capable applications that need local data, reactive queries and a choice of synchronization targets. It is less suitable for a simple browser database whose needs exceed LocalStorage's small-dataset scope but do not justify selecting and configuring another storage option, or for teams that need more than 13 open collections while staying on the Free plan.

Pros and cons

• Pros: Offline operation can work with or without a backend, and sync supports a wide selection of services and protocols.
• Pros: Reactive queries, JSON Schema validation and migrations, plus a password-based encryption plugin, address common application data needs.
• Pros: Broad runtime and storage options let teams choose an environment and persistence approach suited to their application.
• Cons: The Free tier's 13-open-collection ceiling can rule it out for larger collection footprints.
• Cons: LocalStorage is not built for large datasets or heavy writes, so choosing a suitable alternative matters.
• Cons: Pro and Pro Plus are billed annually, and no trial is offered to evaluate paid capabilities first.

Alternatives

For other embedded database options, compare the Embedded Databases list; for a mobile-focused shortlist, see Mobile Databases.

Choose Chroma if its Apache 2.0 open-source database and Chroma Cloud, powered by the same codebase, better match your needs. LadybugDB is a free alternative with an MIT-licensed offering. Pick SQLite for a free embedded SQL database engine with no separate server process or license requirement. bbolt is a free open-source Go library and command-line utility. Consider ObjectBox for its free core database and a free trial. Qdrant offers a free forever cloud tier with a single-node cluster. RocksDB is a free open-source C++ library, dual-licensed under GPLv2 or Apache 2.0. Accessibility Test Framework for Android is another free option.

Verdict

RxDB is a compelling choice for JavaScript developers who need offline-first local data, reactive queries and flexible synchronization across runtimes. Its Free tier is a credible way to start, but the 13-open-collection cap and annual Pro pricing make the intended scale and required storage options central to the decision. Look elsewhere if a narrowly scoped database would serve better or the paid capabilities do not justify the commitment.