Pop-under ads, which are less invasive than pop-up ads, have appeared online since the 1990s and are still used to increase traffic to websites and landing pages by certain ad networks. Pop-under ads are much cheaper and easier to deliver than direct mail ad pieces, and they require a mouse click from the user to close them, which theoretically provides higher-quality ad impressions. Because Internet users are often annoyed by the appearance of pop-under ads, however, their use can be detrimental to the brand.
How Pop-Under Ads Work
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To bypass pop-up blockers, the ads are programmed to launch only when the user has committed some action on the site, such as a mouse click. The ad then appears in a new window, which is hidden behind the original window where the user is currently reading, only to reveal itself when the primary window has been closed. Since the ad opens behind the browsing window, it is often difficult to tell which site launched the ad when multiple browser tabs or windows are open at one time.
Types of Pop-Under Ads
Although Interactive Advertising Bureau guidelines have limited the size and frequency of pop-under ads accepted by most reputable ad networks, there is still plenty of room for creative design when implementing pop-up and pop-under ads.
A graphics pop-under ad displays a simple image file to users when they close the primary window and is the most popular type of pop-under ad. Clicking the image or link takes the user to the advertiser's website or landing page. Graphics-based ads have the smallest file size and are the preferred pop-under format among advertisers.
Animated pop-unders ads use Adobe Flash to allow advertisers to display moving images to consumers. These ads are eye-catching and file sizes are generally lightweight, but they can be slow to render and do not display on devices that are not Flash-compatible, like some smart phones and tablets.
Video pop-unders take the longest time to load and usually require some action on behalf of the user to begin streaming the video, like a mouse click or a mouse roll-over. This emerging format allows advertisers to show 30-second commercials to users without paying high television media prices.
IAB's Pop-Under Ad Guidelines
In order to meet the IAB's ad guidelines, the size of pop-under ads must be either 300 x 200 pixels or 550 x 480 pixels. They must have a maximum initial load size of less than 40 kilobytes, and audio or video must be initiated by the user. Users can be exposed to one pop-under ad per site visit and the ad must be labeled with the advertiser name, the publisher website, and the Web browser.
Web User Acceptance
According to a 2004 report from the IAB, most users do not distinguish pop-up ads from pop-unders and find them both extremely distasteful. Surprisingly, 70 percent of the users surveyed believed pop-under ads had a "very negative effect" on brands, but pop-under ads continue to be in demand among advertisers due to their low cost and favorable conversion rates. In response to the report the IAB created new pop-up and pop-under ad guidelines to reduce ad frequency per user, require specific ad labeling, and meet standard ad size formats.