Two-way vs one-way sync explained
Learn when to use two-way, one-way to Notion, or one-way to provider sync. Includes per-field examples for Google Calendar, Outlook, and Todoist
Two-way sync sends changes in both directions between Notion and your connected app. One-way sync restricts the flow to a single direction: either into Notion or out of Notion. 2sync lets you set sync direction at the automation level and override it per field, giving you full control over how data flows.
What are the sync direction options?
| Direction | Notion changes go to App | App changes go to Notion |
|---|---|---|
| Two-way | Yes | Yes |
| One-way to Notion | No | Yes |
| One-way to Provider | Yes | No |
Two-way sync
Changes flow both directions automatically. Edit an event in Google Calendar and it updates in Notion. Edit the same event in Notion and it updates in Google Calendar.
Best for: Calendar management, task lists you update from both Notion and mobile apps, any workflow where you edit in multiple places.
One-way to Notion
Data flows from the external app into Notion only. Changes you make in Notion stay in Notion and don't push back.
Best for: Email archival from Gmail or Outlook, contact backups, read-only reference databases, logging completed items.
Gmail and Outlook Mail only support one-way to Notion. Two-way email sync is not available.
One-way to provider
Data flows from Notion to the external app only. Notion becomes your single source of truth.
Best for: Drafting events in Notion before publishing to calendar, planning tasks in Notion and pushing to Todoist for mobile access, managing schedules in Notion for team visibility.
Can I set direction per field?
Yes. Each mapped field can have its own sync direction, independent of the automation default.
Example configuration:
| Field | Direction | Why |
|---|---|---|
| Title | Two-way | Edit event names from either app |
| Description | One-way to Notion | Preserve rich formatting from calendar |
| Status | One-way to Provider | Notion controls task completion |
| Organizer | One-way to Notion | Read-only reference field |
To configure per-field direction, open Field Mapping in your automation settings and click the direction arrows next to each field.
Start with two-way sync and then restrict individual fields as needed. This gives you maximum flexibility while protecting specific data flows.
When should I use each direction?
Use two-way when you edit items in both apps regularly. Most calendar and task syncs work best as two-way.
Use one-way to Notion when the external app is your primary input source and Notion is for viewing or reporting. Email sync is always one-way to Notion.
Use one-way to Provider when Notion is your planning hub and external apps are for execution or notification.
Changing sync direction on an existing automation does not delete data. The new direction applies to future changes only. Existing synced items keep their links. See conflict resolution for how 2sync handles simultaneous edits.
For detailed configuration steps, see Sync Direction & Field Mapping.
What should I do next?
Now that you understand sync directions:
- Configure field mapping for your automation
- Set up filters to control what syncs
- Learn how conflicts are resolved
Related
- How sync works for understanding the full sync cycle
- Default values for auto-populating fields on new items
- Delete behavior for controlling what happens when items are removed
- Sync problems for troubleshooting unexpected sync behavior
- Glossary for definitions of sync terminology
FAQ
What is the default sync direction?
When you create a new automation, the default is two-way sync. You can change this during setup or anytime after in the automation settings.
Can I change sync direction after setup?
Yes. Go to your automation settings, open Field Mapping, and adjust the direction at the automation level or per individual field. Changes apply to future sync cycles.
What happens to existing data when I switch directions?
Nothing is deleted or modified. Existing synced items retain their links. The new direction only affects how future changes are handled.
Does one-way sync still detect deletions?
Yes. If you delete an item on the source side, 2sync can remove or archive it on the destination side based on your delete behavior settings.
Can email sync be two-way?
No. Gmail and Outlook Mail sync is one-way to Notion only. You cannot create or send emails from Notion.