ObjectBox

ObjectBox is an embedded database and synchronization system for software that stores data on mobile and IoT devices. It is best suited to teams building offline-capable or decentralized applications. The free database is a strong starting point, but its 1 GB ceiling and separately quoted Sync make scale and deployment important considerations.

Overview

ObjectBox uses a document model with an API query interface, keeping data within an application rather than requiring a separate database server. That design is a practical fit for device-based software that needs local data access, including when connectivity drops. The 1 GB maximum database size is a firm constraint for applications with growing local datasets.

Sync can move data between devices and a backend or server. Teams can run the Sync Server on POSIX systems and cloud providers, but ObjectBox does not offer cloud hosting. That gives deployment control to teams willing to manage the server themselves; it is less convenient for those seeking a hosted service.

Key features

Database capabilities

Native object APIs and object relationships let developers work with application data directly. ACID transactions, reactive observers and automatic schema migration add useful foundations for maintaining consistent, responsive applications as data structures evolve. ObjectBox also supports vector search without a limit on embedding-column dimensions, which may suit applications that need to store and search embeddings.

Synchronization and security

Sync targets offline-first use cases and connects devices with a backend or server. Direct synchronization to MongoDB is supported; connections to other backend databases may require custom work. The Sync Server supports JWT authentication and TLS when supplied with a certificate. Its no-authentication mode is explicitly insecure, so teams should configure authentication and transport security for deployments that need protection.

Languages and current limits

APIs are available for Java, Kotlin, Swift, Flutter/Dart, Go, Python and C/C++, giving teams several ways to adopt the database across application stacks. Mesh Sync is currently available for Android Java/Kotlin and Flutter/Dart starting with version 6.0.0-beta, and its APIs may change before final release. That makes it a beta option rather than a settled basis for production plans.

Pricing

The free database makes it possible to start without a software charge, though the 1 GB size cap matters as local data grows. Sync is priced per project rather than at a published flat rate, so teams should expect to discuss their deployment and support needs before budgeting.

Platforms

ObjectBox supports Android, iOS, Linux, Windows, macOS, Raspberry Pi and POSIX systems. That range covers common mobile and desktop targets as well as embedded-device environments. The company is headquartered in Germany, Europe.

Who it's for

ObjectBox is a good fit for developers building mobile or IoT applications where local data, intermittent connectivity and synchronization across devices matter. It is particularly relevant to decentralized systems made up of restricted devices. Teams that need a larger local database, a managed Sync service, or a backend connector beyond MongoDB without custom integration should weigh those constraints before committing.

Pros and cons

• Pros: The core database is free, with object-oriented APIs, transactions, observers and schema migration included.
• Pros: Sync addresses offline-first movement of data between devices and servers, and the server can be self-hosted.
• Pros: A broad language API selection and vector search support make it adaptable across several application stacks and data use cases.
• Cons: The database is capped at 1 GB, which can rule it out for applications with larger local datasets.
• Cons: Sync requires a project-specific quote, and teams needing hosting must operate their own Sync Server.
• Cons: MongoDB is the directly supported backend database connector; other integrations may need custom development.
• Cons: Mesh Sync remains in beta for the supported language targets, with APIs subject to change.

Alternatives

For more options, browse Mobile Databases or Embedded Databases.

• Espresso is an alternative if the need is Android UI testing rather than an embedded database; its free plan covers a single target app.
• Hive is another free-plan option for teams that can work within its 200MB storage and 10-member workspace limits.
• RxDB is worth considering when web support matters; its free plan includes core functionality, replication and realtime sync, with a limit of 13 open collections.
• Ditto may suit projects that can use its free tier of 10 cloud device connections, 2GB storage and 5GB data transfer, accepting no SLA and limited support.
• Realm offers a free open-source database option; MongoDB acquired Realm and renamed its technology MongoDB Atlas Device SDKs.
• Sparksee may suit academic users able to apply with a valid school or university ID for its free academic licence.
• SQLDelight is a free open-source Kotlin SQL code generation library, rather than a direct match for ObjectBox's database-and-sync offering.
• WCDB is a free open-source mobile database framework for teams seeking that alternative.

Verdict

Choose ObjectBox when a mobile or IoT application needs a local database plus a path to synchronize offline-first data, and your team can operate the Sync Server if necessary. Its free core, broad language support and embedded design are compelling, but the 1 GB cap and project-priced, self-hosted Sync make it a poorer fit for larger datasets or teams that want managed synchronization.