Core database component for the Realm Mobile Database SDKs

What's New

Realm Core v14.3.0



  • Add support to synchronize collections embedded in Mixed properties and other collections (except sets) (PR #7353).
  • Improve performance of change notifications on nested collections somewhat (PR #7402).
  • Improve performance of aggregate operations on Dictionaries of objects, particularly when the dictionaries are empty (PR #7418)
  • Added Resumption delay configuration to SyncClientTimeouts. (PR #7441)


  • Fixed conflict resolution bug which may result in an crash when the AddInteger instruction on Mixed properties is merged against updates to a non-integer type (PR #7353).
  • Fix a spurious crash related to opening a Realm on background thread while the process was in the middle of exiting (#7420)
  • Fix a data race in change notification delivery when running at debug log level (PR #7402, since v14.0.0).
  • Fix a 10-15% performance regression when reading data from the Realm resulting from Obj being made a non-trivial type (PR #7402, since v14.0.0).

Breaking changes

  • Remove realm_scheduler_set_default_factory() and realm_scheduler_has_default_factory(), and change the Scheduler factory function to a bare function pointer rather than a UniqueFunction so that it does not have a non-trivial destructor.


  • Fileformat: Generates files with format v24. Reads and automatically upgrade from fileformat v10. If you want to upgrade from an earlier file format version you will have to use RealmCore v13.x.y or earlier.


  • The CMake option REALM_MONGODB_ENDPOINT for running the object-store-tests against baas has been deprecated in favor of an environment variable of the same name (PR #7423).
  • The object-store-tests test suite can now launch baas containers on its own by specifying a BAASAAS_API_KEY in the environment (PR #7423).

Latest Release Coverage Status Source License


Realm is a mobile database that runs directly inside phones, tablets or wearables - check out

This repository holds the source code for the core database component used by all the Realm Mobile Database products:

Realm Core is not in itself an "end-user" product with a publicly stable and supported API.

Refer to the Realm documentation for information about Realm and using the SDKs.

Building Realm

How to build Realm Core is described here.


See for more details!

Code of Conduct

This project adheres to the MongoDB Code of Conduct. By participating, you are expected to uphold this code. Please report unacceptable behavior to


Realm Core is published under the Apache 2.0 license.

See the THIRD-PARTY-NOTICES file for licenses related to included third party libraries.


Feedback to the Realm SDK's should be given in the respective SDK's github mentioned in the top of this readme. For anything specifically about Realm Core, please create an issue here.


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Last updated: Fri Apr 12 2024 18:05:40 GMT-0900 (Hawaii-Aleutian Daylight Time)