On the heels of Google's $390 million acquisition of ad-tech company AdMeld, funds are flowing freely into the digital-ad buying-sector as startups on both the buy- and sell-side of online advertising gear up for more M&A activity.

MediaMath, a top digital media-buying platform, just closed $20 million of funding, bringing its total capitalization to $30 million. The New York-based startup, which bills itself as the "Bloomberg terminal for marketing," licenses its technology to top agency holding companies and media buyers such as Publicis, WPP, Cadreon and Starcom so they can bid on ad space across exchanges such as Yahoo's Right Media, Google's AdEx and Microsoft's AdECN.

Altogether, MediaMath's buying terminal transacts tens of millions in online ad spending each month, said its CEO, Joe Zawadzki. The company also offers buying on Facebook through a partnership with Clickable and Spruce Media, though MediaMath says the next version of its buying dashboard will plug directly into Facebook's ad platform.

The latest Series B round of funding was led by publicly traded venture fund Safeguard Scientifics along with Catalyst Investors and Observatory Capital. Jonathan Perl of Observatory and Ryan McNally of Catalyst will join MediaMath's board as part of the round.

"We regard MediaMath as extremely well-positioned to not just take advantage of brand dollars moving online, but to continue leading the trend of brands utilizing mathematically-driven analytics," Safeguard Managing Director Erik Rasmussen said in a statement. "We are seeing significant growth in the heavier lifting of brand building for buyers through MediaMath's technology and relationships."

Mr. Zawadzki said the investment will be used to maintain majority employee ownership as well as expand its buying services into video ads, social ads and mobile.

"It allows us to move beyond our original platform to include these other venues," he said. "As more media types become more digital you now need to have a centralized approach to analytics and buying."

Mediamath's competitors include Turn, x+1, Dataxu and Google's Invite Media, all helping marketers buy and optimize online ad spots in real time. Google bolstered its offerings with a bid to buy Admeld, which represents the publisher side of the ecosystem, awaiting Department of Justice approval.

Google bought MediaMath competitor Invite Media last year and is increasingly building out a system that connects buyers and sellers of online ads to exchanges, analytics and other technologies. But that doesn't concern Mr. Zawadzki. He said Google is , actually, a client, and though he declined to specify which services Google uses, he suggested MediaMath was able better find premium placements for brand advertisers.

"Our thesis is best interoperability," Mr. Zawadzki says. "Rather than buying an AdMeld, we partner more deeply with AdMeld and Rubicon and Pubmatic."

The 140-person company has recently expanded offices into London, Boston, Chicago, Los Angeles and San Francisco and has worked with large brand advertisers such as American Express, Kayak and Gilt.