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Cookie synchronization offers a way to associate 3rd-Party Cookie IDs to a [User's Profile](https://docs.audience.kevel.com/collect/user-ids). These IDs can later be used by some [Destinations](https://docs.audience.kevel.com/activations/user-data-destinations).

## CookieSync Providers

CookieSync Providers represent 3rd-Party ID data sources which will be integrated with the Kevel Audience via cookie synchronization. After a provider is created, the cookie synchronization integration can be started, and these IDs can be used to activate users to some [Destinations](https://docs.audience.kevel.com/activations/user-data-destinations).

The following fields are available:

- **Name**: Name for the CookieSync Provider.
- **ID**: Identifier for the CookieSync Provider. It is used later to perform cookieSync for this specific provider.
- **Active**: Enables/disables integrations with this CookieSync Provider.
- **URL for cookie synchronization**: If no 3rd-party ID (`uid` field) is received in the cookieSync request, the request will be redirected to this URL to synchronize our ID with the 3rd-Party provider. This field supports templating using the liquid template language, and the user ID can be interpolated using the `{{ meta.USER_ID }}`. This field can be left empty if you only plan to perform cookie synchronization while knowing the 3rd-Party ID.

Example: `https://thecookiesync.com/sync?id={{ meta.USER_ID }}`.

## Cookie Synchronization

The cookie synchronization process has 2 variants:

- **The CookieSync Provider provides a 3rd-Party Cookie ID**:

With this approach, every cookie synchronization request will send the 3rd-Party ID which will be stored in Kevel Audience directly. Any activation using this CookieSync Provider User ID will use this ID.

- **The CookieSync Provider doesn't provide a 3rd-Party Cookie ID**:

In this approach, requests will be sent without the unknown 3rd-Party Cookie ID. To create the mapping between the 2 systems, the request will be redirected to the 3rd-Party with a unique ID generated by Kevel Audience for that user. Any activation using this CookieSync Provider User ID will use this ID.

With this approach, the **URL for cookie synchronization** must be defined in the [CookieSync Provider](https://docs.audience.kevel.com/collect/cookiesync#cookiesync-providers) configuration.

To perform cookie synchronization we provide 2 approaches:

- **Via JavaScript tag**: After [including the tag](https://docs.audience.kevel.com/platform-guides/js-tag#including-the-tag) in your website, you can perform cookieSync requests by following the instructions in [Using the tag - CookieSync](https://docs.audience.kevel.com/platform-guides/js-tag#cookiesync).

- **Via HTTP API**: See the [API reference](https://docs.audience.kevel.com/api/http/match-activator) for details.