SAN FRANCISCO – Instagram, long the favorite domain of teenagers, has become big business for small companies, Social Media & Marketing Daily reports. The photo- and video-sharing application has experienced a growth spurt, with monthly U.S. users rising 35% in 2013, according to eMarketer. Instagram now roughly has the same number of users as Twitter on desktop computers and more U.S. users via smartphones.

“We’ve been blown away by the volume of photos,” said Perry Evans, CEO of Closely, which analyzes social media for small businesses. While Instagram and parent company Facebook registered about the same number of posts on average over a 30-day period, Instagram edged ahead in engagement levels.

For example, Instagram had a higher average number of likes and comments than Facebook. For small businesses, an important plus is users more often put up Instagram’s tagged images; on Facebook, it’s the company doing the majority of the postings.

While it’s always tricky to open up your company to potentially negative reviews or comments, Evans said that most of the images posted are good marketing tools for the business. Instagram faces increased competition as Twitter announced the ability for users to tag pictures, as well as a new app that will allow users to post up to four photos per tweet.