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guides/two-way-sync.md

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+# Two-Way Sync
+
+Two-way sync in WatchState helps keep your `play progress` and `watch state` synchronized across multiple backends. It’s called "many-to-many" sync, meaning you can sync data between several backends, and they all stay up to date with each other. This sync is powered by WatchState's `import` and `export` features.
+
+# Use Cases
+
+- If you watch a show on Plex and want to continue it on Jellyfin or Emby, two-way sync ensures your progress is saved.
+- Keep your media backends synced so you always know where you left off.
+
+# How Sync Works
+
+WatchState first pulls the latest play and progress information from your backends, then stores it locally this is the `import` process. The system checks to ensure the data is up-to-date, and older data is saved as metadata without overriding the most current watch state.
+
+On the export side, we compare the backend's last sync date with any local changes. From there, we create a list of items that need updating for each backend. If there are only a few changes, we trigger a quick sync operation `push mode`. If the changes are more extensive, we perform a full export, which compares all remote data with the local data. This full export only happens when there are many changes and/or metadata is missing from the backend, which is why it's crucial to keep the `Import data from this backend?` or, at a minimum, the `Import metadata only from this backend?` option enabled.
+
+# Setting Up Two-Way Sync
+
+To set up two-way sync, follow the steps below:
+
+### Step 1: Setting Up The Backends.
+
+First, make sure you have completed the [one-way sync guide](/help/one-way-sync) to get your backends synced.
+
+### Step 2: Enable Sync Sliders.
+
+Go to the <!--i:fa-server--> *Backends* page. Here, you'll see two sliders for each backend: `Import` and `Export`.
+
+- The `Import` slider brings data from the backend into WatchState.
+- The `Export` slider sends data from WatchState to the backend.
+
+When you're sure the data looks correct, turn on the `Export` slider for your main backend and the `Import` slider for the others. This will keep your backends synced.
+
+# Enable Scheduled Tasks
+
+If everything looks good and you want WatchState to automatically sync your backends, do the following:
+
+Go to the <!--i:fa-tasks--> **Tasks** page. Enable the two tasks by toggling the sliders next to `Import` and `Export`.
+
+### Tuning The run schedule
+
+To control how often these tasks run, go to the <!--i:fa-cogs--> **Env** page, click the <!--i:fa-plus--> **Add** button, and select the environment variables `WS_CRON_EXPORT_AT` and `WS_CRON_IMPORT_AT`. These variables use CRON timer expressions. For example, if you want the export task to run every 6 hours, set `WS_CRON_EXPORT_AT` to `0 */6 * * *`. For more help with CRON expressions, visit [crontab.guru](https://crontab.guru/).
+
+> [!IMPORTANT]  
+> The `Import` task can be resource-intensive, especially for large libraries. It may take some time to complete and could use a lot of CPU power. It’s recommended to run it a few times a day, with every 6 hours being a good starting point.
+
+# Enable Webhooks
+
+For even faster sync operations, you can enable webhooks. For more details, check out the [webhooks guide](/help/webhooks).
+
+# Troubleshooting
+
+TBA