Exchanges and data providers initiate cookie syncing with Basis DSP where possible on their own footprint—that is, pages on which their code executes. In addition, Basis DSP initiates cookie syncs when serving ad impressions, as well as in our audience and conversion scripts. This ensures that campaigns targeting audiences—first- or third-party—are able to achieve maximum scale, as exchange or data provider-initiated sync alone may not reach all users.
Regardless of this, some advertisers may have a policy of not allowing third-party pixels to be fired on their sites. If this is the case, you can use the HTML image option instead of the script option for your audiences and conversions. The two options are functionally identical except that the script option also includes cookie syncs. It is not recommended to use the HTML image option unless it is necessary as it may have a negative impact on campaign scale since it is necessary for users to be synced at other opportunities (exchange/data provider initiated, or when Basis DSP serves impressions) for audience-targeted campaigns to spend.