• by Gavin O'Malley  @mp_gavin, May 12, 2015

Facebook is happy with the performance of its “carousel” ads -- so much so that’s it is expanding the multi-image format to mobile.

On mobile, the carousel format can support up to five images with links, a Facebook spokeswoman said on Monday. “Mobile app install and engagement ads in the carousel format are available now through the ads API,” she said.

Facebook is also offering to optimize the order of the links, based on engagement and expected performance. “This optional feature has helped increase click-through rates by an average of 12%,” a Facebook spokeswoman said.

Since Facebook debuted the ads -- which encourage users to swipe for more branded content -- they have driven 30% to 50% lower cost-per-conversion, and 20% to 30% per lower cost-per-click than single-image link ads, according to the social giant.

Among other success stories, Neiman Marcus has seen 300% higher conversion rates with carousel ads than with other Facebook ad units.

Foodpanda, meanwhile, increased click-through rates by 180%, and reduced its cost-per-impression by 39% using carousel ads.

Following a soft launch, Facebook’s Instagram unit recently rolled out carousel ads to a broader audience. Initial brands included Showtime, Banana Republic, Old Navy, L'Oreal Paris, and Samsung. Later in the “carousel,” the units also serve a link to brands’ mobile sites. This feature is particularly appealing to retail brands. Among other efforts, Instagram recently rolled out verified badges for brands, as well as celebrities and athletes.

“Creating relevant content for our customers, while also making it easier for them to shop, is a win-win,” Aimee Lapic, Banana Republic senior vice president/GM of customer experience, said last month.

Likening them to a multi-page print campaign, Instagram is counting on the ads to turn its current popularity into profits. Sensitive to user tastes and privacy concerns, however, Instagram has taken a cautious approach to advertising.

Still, at the risk of alienating users, Instagram parent Facebook has been steadily introducing new opportunities for advertisers to show off their wares. The social giant recently unveiled Product Ads -- a format for brands to show off multiple product offerings, and in some cases, their entire inventory.