> For the complete documentation index, see [llms.txt](https://wiki.crosswatch.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.crosswatch.app/crosswatch/settings/synchronization.md).

# Synchronization

Synchronization adapters are the “connectors” the orchestrator uses for syncing. Each adapter knows how to read a provider and how to write changes back.

Related: [CW Orchestrator](broken://spaces/3rh5THg1PdhVsBt3GALo/pages/458ZbsIKcwSYg9y6eb8R).

{% hint style="success" %}
If a provider behaves unexpectedly, start with its adapter page.
{% endhint %}

{% hint style="info" %}
Start with one pair and one feature. Expand only after the first run is clean.
{% endhint %}

### How to use this section

{% stepper %}
{% step %}

### Connect providers

Use [Authentication](broken://spaces/3rh5THg1PdhVsBt3GALo/pages/XXSROEx2Yqy98k1SqJvO).
{% endstep %}

{% step %}

### Build a pair

Create one pair and enable one feature.
{% endstep %}

{% step %}

### Check adapter behavior

If a provider acts oddly, open its adapter page.
{% endstep %}
{% endstepper %}

### What adapters do

Adapters implement the same core flow:

* **Index**: fetch a present-state snapshot (what exists now).
* **Normalize**: turn provider rows into common items + stable IDs.
* **Apply**: add/remove/update on the target side.
* **Stabilize**: use local state to avoid repeats and flapping.

### Feature semantics (how to think about “changes”)

* **Watchlist**: set-like. Adds and removes are straightforward.
* **History**: event-like. `watched_at` matters. Duplicates are common.
* **Ratings**: numeric. Scale differences matter. Deletes can be destructive.
* **Playlists**: ordered. Often provider-specific. Not widely supported yet.

### Stability knobs (common patterns)

* Snapshot caching to reduce API load.
* Chunking + small pauses to avoid rate limits.
* Shadow/unresolved files to prevent endless retries.
* Activity/watermark logic for delta providers (example: SIMKL).

### Adapter guides

<table data-view="cards"><thead><tr><th>Adapter</th><th data-card-target data-type="content-ref">Open</th></tr></thead><tbody><tr><td>Plex</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/OWAe360aTxSHXAnIiRoW">/spaces/3rh5THg1PdhVsBt3GALo/pages/OWAe360aTxSHXAnIiRoW</a></td></tr><tr><td>Jellyfin</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/LVxifNNcUFwNIcZzn53r">/spaces/3rh5THg1PdhVsBt3GALo/pages/LVxifNNcUFwNIcZzn53r</a></td></tr><tr><td>Emby</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/cHaK7elcPSgvo1VR2E48">/spaces/3rh5THg1PdhVsBt3GALo/pages/cHaK7elcPSgvo1VR2E48</a></td></tr><tr><td>Nuvio</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/FvjpLwNX009lgZoh3kcm">/spaces/3rh5THg1PdhVsBt3GALo/pages/FvjpLwNX009lgZoh3kcm</a></td></tr><tr><td>Trakt</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/bRhLnM3fO7uDpCByQXcs">/spaces/3rh5THg1PdhVsBt3GALo/pages/bRhLnM3fO7uDpCByQXcs</a></td></tr><tr><td>SIMKL</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/eqXoLy9ij0AlCf3sbYdg">/spaces/3rh5THg1PdhVsBt3GALo/pages/eqXoLy9ij0AlCf3sbYdg</a></td></tr><tr><td>MDBList</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/CsNqeI2L3uOOXg95AW06">/spaces/3rh5THg1PdhVsBt3GALo/pages/CsNqeI2L3uOOXg95AW06</a></td></tr><tr><td>PublicMetaDB</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/IgNgLWcDb9O2aYI59Nax">/spaces/3rh5THg1PdhVsBt3GALo/pages/IgNgLWcDb9O2aYI59Nax</a></td></tr><tr><td>AniList</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/GUWl5kpWjOzbTroJ9EC0">/spaces/3rh5THg1PdhVsBt3GALo/pages/GUWl5kpWjOzbTroJ9EC0</a></td></tr><tr><td>Tautulli</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/7R7JVYBKElUh131kNRvA">/spaces/3rh5THg1PdhVsBt3GALo/pages/7R7JVYBKElUh131kNRvA</a></td></tr><tr><td>CW local backup</td><td><a href="/spaces/3rh5THg1PdhVsBt3GALo/pages/wo1bvQ75vjpmwdLU5SbB">/spaces/3rh5THg1PdhVsBt3GALo/pages/wo1bvQ75vjpmwdLU5SbB</a></td></tr></tbody></table>

### Troubleshooting quick checks

* **Adds keep reappearing**: provider didn’t “stick” the write. Check adapter state files.
* **Recent changes not syncing**: reduce caching, or force a fresh read if supported.
* **429 / 5xx errors**: reduce chunk size, add delay, run less often.
* **Mismatches**: add [Metadata / ID Mapping](/crosswatch/settings/connections/metadata.md) and prefer stable IDs.

### Related topics

* [Configure Pairs](/crosswatch/settings/configure-pairs.md) — step-by-step pair setup.
* [Best practices](/getting-started/best-practices.md) — safe defaults.


---

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