(CNBC) - Facebook's Instagram app just hit a major milestone: It now has more than 200,000 monthly active advertisers, paying to reach its 400-million-plus active users.
That 200,000 number is up from just "hundreds" of advertisers in June. The company, which opened its self-service ad platform in September, said 75 percent of its advertisers are outside the U.S. and the vast majority are small and medium-sized businesses.
And this new scale means a better experience for users, and a better return for advertisers.
"Having 200,000 advertisers gives us an ability to better tailor the ads that people see to their likes and interests," said James Quarles, Instagram's global head of business and brand development. "The more advertisers we have, the more relevant the ad, the better the ad experience."
Perhaps what's most striking about Instagram's advertiser numbers is how they compare to Twitter's.
In its last earnings report, Twitter said it has 130,000 advertisers, four years after the company opened its self-serve ad platform.
Instagram has a built-in advantage in helping it expand its advertiser numbers quickly: Facebook's massive advertiser base — 2.5 million strong — can easily tack on the purchase of Instagram ads.
Ninety-eight of the top 100 Facebook advertisers are also on Instagram. "We recommend that businesses be both on Facebook and on Instagram — it's the same back end, but a different storefront," said Quarles.
Instagram is also sharing statistics showing the effectiveness of its format. About half of its users already follow businesses, making the addition of posts from brands a natural addition to the news feed. The company also said 60 percent of users say they learn about products and services on Instagram, and 75 percent say they take action after being inspired by an Instagram post — like visiting a website, searching, shopping or telling a friend. Plus, there's the statistic that Facebook has put out there for a while: One in 5 mobile minutes is spent on Facebook and Instagram. And it recently announced that over the last six months, the time people spent watching videos on Instagram increased by more than 40 percent.
With Facebook's advertiser base, and Instagram's recently launched 60-second video ads, expect Instagram to make a growing impact on Facebook's bottom line.