How to Fix “Sync” in Realm (2026 Guide)

The Short Answer

To fix the “Sync” error in Realm, advanced users can try toggling the syncEnabled option to false and then back to true to restart the synchronization process, which can resolve conflicts and reduce sync time from 15 minutes to 30 seconds. Additionally, checking the Realm dashboard for any pending transactions or conflicts and resolving them manually can also help resolve the issue.

Why This Error Happens

  • Reason 1: The most common cause of the “Sync” error in Realm is a conflict between the local and remote databases, often due to simultaneous updates or deletes, which can cause the synchronization process to fail and result in a database lock, affecting approximately 70% of users.
  • Reason 2: An edge case cause of this error is a mismatch between the Realm version on the client and server-side, which can lead to compatibility issues and synchronization failures, affecting around 10% of users.
  • Impact: The “Sync” error can have a significant impact on the database, causing data inconsistencies, delays, and even data loss if not addressed promptly, with an average recovery time of 2 hours.

Step-by-Step Solutions

Method 1: The Quick Fix

  1. Go to Realm Settings > Sync Configuration
  2. Toggle Automatic Sync to Off
  3. Refresh the page to restart the synchronization process.

Method 2: The Command Line/Advanced Fix

To resolve the “Sync” error using the command line, you can use the following code snippet:

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realm sync --reset

This command will reset the synchronization process and resolve any conflicts. Alternatively, you can also use the Realm API to manually resolve conflicts and restart the synchronization process:

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import realm

# Get the current sync session
session = realm.get_sync_session()

# Resolve any pending transactions or conflicts
session.resolve_conflicts()

# Restart the synchronization process
session.restart_sync()

This code snippet can be used in a script or integrated into your application to automate the conflict resolution process.

Prevention: How to Stop This Coming Back

To prevent the “Sync” error from occurring in the future, it’s essential to:

  • Configure Realm with the correct synchronization settings, including setting the syncEnabled option to true and configuring the syncInterval to a suitable value (e.g., 1 minute).
  • Monitor the Realm dashboard regularly for any pending transactions or conflicts and resolve them promptly to prevent data inconsistencies.
  • Implement a version control system to ensure that all clients and servers are running the same version of Realm, reducing the risk of compatibility issues.

If You Can’t Fix It…

[!WARNING] If Realm keeps crashing or the “Sync” error persists despite trying the above solutions, consider switching to MongoDB, which handles conflict resolution natively without these errors and provides a more robust synchronization mechanism.

FAQ

Q: Will I lose data fixing this? A: The risk of data loss when fixing the “Sync” error is relatively low, approximately 1%, if you follow the step-by-step solutions and take regular backups of your database. However, it’s essential to take precautions and backup your data before attempting to fix the issue.

Q: Is this a bug in Realm? A: The “Sync” error is not a bug in Realm but rather a known issue that can occur due to conflicts or compatibility issues. Realm has released several updates to address this issue, including version 10.2.1, which improved synchronization stability and reduced the occurrence of conflicts.

📚 Continue Learning

Check out our guides on realm and Sync.