iOS app discovery service AppGratis is the most used discovery app among iPhone users, according to Onavo, a company that tracks data usage for users. Discovery apps have become a platform for other mobile developers to get their apps to stand out from the combined 1.5 million apps on the Apple App Store and Google Play. These discovery apps promote a paid app by featuring it for free or at a steep discount for a limited time. Paris-based AppGratis grabbed a 4.6 percent share of iPhone users as of February, which Onavo defines as the percentage of U.S. iPhone users who, within a 30-day period, open an app at least once.

AppAdvice.com’s Apps Gone Free, which is known for allowing the community to give their input as to what paid apps Apps Gone Free should offer for free, nabbed a 1.9 percent share of the market, and held steady at that mark for the past three months. Appsfire held down market share of iPhone users in the past three months, with a slight bump in market share in January. AppTrailers, where users can watch video trailers of apps and get rewarded for it, fell in market share over the past three months, from a 1.3 percent market share of iPhone users to 1 percent.

Smaller app discovery services like FreeAppADay grew its market share in the past three months from .4 percent to .75 percent and Appoday barely moved the needle from .62 percent to .69 percent.

Onavo is able to collect usage data on apps because its two free consumer apps, Onavo Extend and Onavo Count, monitor app data usage for users. Onavo anonymously collects that usage data of third-party apps from the millions of users who have downloaded and use Extend or Count on their mobile device.