ObjectBox C / C++ Database

This is the ObjectBox documentation for our C and C++ APIs. We strive to provide you with the easiest and fastest solution to store and retrieve data.

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Latest Versions (Changelogs)

0.21.0 (2024-02-13)

  • In-memory databases (simply provide a "memory:" prefixed "directory")


  • New client/server statistics API

  • New server API to enable authenticators

  • Sync server: support for sync permissions, blocks client updates with no write permission

  • Added sync-level login/write permissions for Admin Users DB and Web-UI

  • New authenticator "ObjectBox Admin" with support for authorization

  • New client API for username/password credentials

  • New client-side error listener API; initially reports "receive-only" downgrade due to no write permissions.

0.20.0 (2023-12-11)

  • Added OBXFeature_Backup to query for the feature's availability

  • Internal: added a DB store abstraction layer (another announcement about this will follow)

  • Tree API: fix for meta IDs vs. IDs

  • Various internal improvements


  • Sync clients may now supply multiple URLs; for each connection attempt a random one is chosen. This allows for client-side load balancing and failover with an ObjectBox Sync cluster.

0.19.0 (2023-09-04)

  • New K/V validation option on opening the store

  • Additions cursor API: get current ID, ID-based seeks (seek to first ID, seek to next ID)

  • Support scalar vector types with basic queries (APIs only, no generator support)

  • Various tree API improvements, e.g. introspection

  • Minor API clean up: e.g. using int types for bit flags not enums

  • Fixes query link condition in combination with some "or" conditions

  • Fixes query "less" condition for case-sensitive strings with value indexes (default is hashed index)

  • Updated Linux toolchain; now requires glibc 2.28 or higher (and GLIBCXX_3.4.25); e.g. the following minium versions are fine: Debian Buster 10 (2019), Ubuntu 20.04, RHEL 8 (2019)

  • Various internal improvements

  • Sync: various additions and improvements (client and server)

0.18.1 (2023-01-30)

Recommended bugfix release; please update.

  • Fixes "Could not put (-30786)", which may occur in some corner cases on some platforms.

0.18.0 (2022-10-31)

  • Date properties can now be tagged as expiration time; which can be then be easily evicted

  • Tree API: various additions and improvements, e.g. OBXTreeOptionFlags to configure the tree behavior

  • New query condition to match objects that have a given number of relations

  • New "max data size" store setting

  • Enabled stricter compiler settings

  • Added stacktraces on errors (Linux only; very lightweight as it uses external addr2line or llvm-symbolizer)

  • Added log callback for most important logs

  • Consolidated "user data" passing as the last parameter

  • Various internal improvements


  • Added BoxTypeless, QueryBuilderBase and QueryBase: these can be used without generated code and template types.

  • New APIs to get the schema IDs for entity types and properties

  • Added two methods to Store to await asynchronous processing

  • Added "internal" namespace so that internal members do not spill into the obx namespace

  • Move more implementations to OBX_CPP_FILE


  • Custom protocols for Sync: plugin your own messaging protocol, which ObjectBox Sync will run on

  • Improvements to run Sync Server with limited disk space (e.g. on small devices)

  • Tree Sync improvements; e.g. consolidate conflicts

  • WebSockets (sync protocol) is now a feature, which can be turned off (special build version)

  • Performance optimizations

0.17.0 (2022-06-15)

  • Added a "weak store" API providing weak reference for stores (typically used by background threads)

  • Added Store ID API, e.g. getting a store by its ID

  • Various internal improvements including minor optimizations for binary size and performance


  • New "OBX_CPP_FILE" define to place declarations in a single .cpp/.cc file: improves compilation time and results

  • New "Exception" base class for all thrown exceptions

  • Various internal improvements, e.g. a "internal" namespace to better distinguish from userland API

0.16.0 (2022-05-06)

  • Allow UTF-8 for database directories on Windows (available for other platforms before)

  • Various internal improvements


  • Promoted Options to a top level class, as nested classes cannot be declared forward

  • New #define to disable FlatBuffers includes to simplify new project setup

  • Rename Exception to DbException

  • Minor improvements

V0.15.2 (2022-02-15)

  • Add store cloning

  • Fix attaching to a reopened store

V0.15.1 (2022-01-26)

  • Fix non-unique indexes triggering unique constraint violations in corner cases (requires at least two unique constraints in an entity and a specific order; introduced in 0.15.0)

  • Admin UI now supports multiple sessions to the same host using different ports (session ID via HTTP request)

  • Minor performance improvements with hashed indexes


  • Performance improvements for compression and decompression

V0.15.0 (2021-12-09)

  • New "Flex" data type that can contain data of various types like integers, floating points, strings, lists and maps

  • New query conditions for Flex lists to find a specific element

  • New query conditions for Flex maps to find elements with a specific key or key/value pair

  • New unique on-conflict strategy: replace conflicting objects (OBXPropertyFlags_UNIQUE_ON_CONFLICT_REPLACE)

  • New functions to attach to existing stores using only the file path (in the same process)

  • New APIs for ObjectBox Admin, the web based UI (formerly known as Object Browser): obx_admin_*

  • Minor performance improvements for indexed access

  • Major performance improvements for tree/GraphQL queries

  • ARM binaries are now built for minimal size reducing the library size significantly

  • New "no_reader_thread_locals" store option

  • Enable debug logging (requires a special build)

  • API: Type for query offsets and limits was changed from uint64_t to size_t

  • API: rarely used obx_txn_mark_success() was removed; use obx_txn_success()

  • API: feature checks consolidated to only use obx_has_feature()

  • Many internal improvements

  • Core version 3.0.1-2021-12-09


  • New API for embedded server mode: obx_sync_server_* (implementation available on request)

Earlier Versions

The changelogs of earlier versions are available as part of the GitHub releases.

Provides native dynamic/shared library (.so/.dylib/.dll)

  • Provides C & C++ headers (objectbox.h & objectbox.hpp)

ObjectBox Generator

Check the ObjectBox Generator releases for details.

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