Hi Meir,
Thanks for reaching out. There isn't an setting in the API for restricting display campaign ad placements to YouTube and a display campaign must have its AdvertisingChannelType set to 'display'. However, if you have seen such a setting supported in the Ads UI, we can submit a feature request on your behalf.
You can also specify
youtube.com placements using the CampaignCriterionService. If you are not using the API, I would recommend looking through
this general support article.
Regards,
Matt
Google Ads API Team
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