What is Pop-Under?
A pop-under ad opens a new browser window behind the current one and remains concealed until the user closes or minimizes the window in use. Less annoying than pop-ups, pop-unders still offer full-screen advert space without interrupting the browsing activity. Marketers focus on them for retargeting and brand awareness, but modern browsers and ad blockers increasingly restrict them due to user-experience concerns. Because of this, they are less used nowadays.
Examples of pop-unders include e-commerce promo windows that open behind product pages, survey invitations that launch beneath news articles, and video ads that load behind the main browser tab after page load.
Related terms: under ads, background ads, retargeting, ad blocking