# Watchlist API key features

Caplin Trader’s Watchlist API introduces a new model for managing watchlists that enables watchlists to be synchronised in real time between a user’s devices.

The new model has moved responsibility for the persistence of watchlist configurations from [Webcentric](../webcentric/index.md) to [Transformer](../../../caplin-platform/transformer/index.md), from where they may be shared in real time between supporting [StreamLink](../../../caplin-platform/streamlink/index.md) clients.

## The two watchlist models contrasted

The table below contrasts the original Webcentric-persisted model with the new Transformer-persisted model.

|     |     |     |
| --- | --- | --- |
|  | Webcentric-Persisted Watchlists | Transformer-Persisted Watchlists |
| **Client-side interface** | Webcentric’s layout XML | Watchlist API |
| **Persistence store** | Webcentric’s layout XML and the Webcentric database. | Private containers hosted on Transformer and persisted by Transformer’s Persistence Service. |
| **Role of Webcentric** | Webcentric stores the full definition of a watchlist within the layout XML of a [Grid](../../3/grid/index.md). | Webcentric stores only the ID of the Transformer-hosted watchlist within the layout XML of a [Grid](../../3/grid/index.md). |
| **Role of Transformer** | Transformer hosts a watchlist’s content in a temporary container that exists only for the duration that the watchlist is displayed in a [Grid](../../3/grid/index.md) | Transformer hosts a watchlist’s metadata and content in containers that are persistent across user sessions and server restarts |
| **When watchlists are persisted** | When the Webcentric layout is saved by the user | Immediately |
| **Lifespan of a watchlist’s subject container on Transformer** | Temporary. Exists for the duration of the user session only. | Permanent. A watchlist persists across user sessions until the user deletes the watchlist. |
| **Namespace of watchlist containers on Transformer** | `/WATCHLIST/...` | `/PRIVATE/WATCHLIST/...` |
| **Client support** | Caplin Trader only | Any StreamLink client with support for Transformer-persisted watchlists |
| **When watchlist configurations are read by Caplin Trader** | Once, when the Webcentric layout is loaded | Clients subscribe to live configurations on Transformer and receive updates in real time |

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**See also**:

* [Watchlist API design](watchlists-watchlist-api-design.md)
* How can I... [Migrate to the Watchlist API](watchlists-migrate-to-the-watchlist-api.md)