In today’s media ecosystem, advertisers face the challenge to create ad campaigns with the ability to engage consumers and ultimately increase conversions. Hence, they need guidance on how to design promising ad copies and on which websites to deliver these ads. In this study, the authors analyze how different message content and ad format elements influences consumers’ likelihood to click on an ad and subsequently convert on the advertising website. Additionally, they explore the effects of placing an ad on different websites. The main results suggest that message content and ad format that enhance engagement do not necessarily enhance conversions. Furthermore, several novel findings pertain to placement in social media and use of influencer marketing: display ads are effective on social media, especially with hard sell messages. Influencer ads increase engagement more than conversion and are more effective outside social media. A simulation reveals the impact of optimizing ad copy and placement decisions: optimizing ad copy decisions has larger effects than placement decisions and synergy exists between both decisions, offering further guidance to managers.