Facebook Inc said on Tuesday that its active advertisers rose to 2 million, a 33 percent increase from the 1.5 million it had in July 2014.

The vast majority of the advertisers, defined as those that have placed an ad on the social media platform in the last 30 days, represent small- and medium-sized business owners.

"Small business owners are really hard to reach and they are not tech savvy usually," Facebook's chief operating officer, Sheryl Sandberg, said in an interview. She added that 30 million small business owners have Facebook pages.

Facebook also launched a mobile app for advertisers to use to manage their campaigns.

Of Facebook's newly acquired advertisers in the 2014 fourth quarter, 80 percent started by paying for a promoted post.

Facebook does not break out the actual number of small business advertisers versus big brands, but they tend to spend on average $5 to $50 a day. That compares to the millions spent annually by big companies.

Sandberg said that the fastest areas of growth of small business advertising are in regions of Europe-Middle East-Africa and Asia Pacific.

Getting more advertisers onto its platform is critical for Facebook as it tries to increase global share. Facebook's fourth-quarter revenue grew 49 percent to $3.85 billion from the same period a year ago, with mobile accounting for 69 percent of advertising revenue.

Google is the worldwide leader in digital advertising market share, at 31.1 percent, according to estimates from research firm eMarketer. But Google's slice has shrunk slightly, down from 33.6 percent in 2013.

Facebook, on the other hand, increased its share to 7.8 percent in 2014 from 5.8 percent in 2013, according to eMarketer.

It is unknown how many advertisers Google currently has. In 2007, it said it was used by 1 million advertisers.

Padraig Bracken, marketing manager at Y-Volution, a Dublin-based toy company that makes scooters for kids, said he plans to spend 60 percent of his digital marketing budget with Facebook this year.

"Facebook is pushing a lot harder than Google," he said. "Google search is the king but it's getting more expensive."

Kay Martinovic, who owns Kay's Designer Consignment in Ormond Beach, Florida, said that it is so easy to target potential customers that she trimmed her spend with the platform to $4,200 in 2014 from $9,000 in 2013.