Downloads of Facebook’s app on Google Play in the U.S. are trending down over the past weeks, although the app is still the most-downloaded app on Android. But on iOS, Facebook has dropped from the 51st-most-downloaded app in mid-July to the 70th.

Those are just two of the stats are are now available in a new offering from Distimo: App Trends.

The data’s not perfect, and Distimo isn’t specific about exact download numbers. Plus, it’s only a two-week snapshot. But it is available for all apps in Google Play and the iOS App Store, and it has one other massive redeeming virtue: It’s completely free.

In fact, App Trends is the first freely available global service that provides download and revenue trends for all apps.

App Trends - CSR Racing

“Our new App Trends service provides a new degree of transparency to the mobile app market that has not been easily accessible to users before, and offers true insight into an app’s uptake and success over time,” Distimo CEO Vincent Hoogsteder said in a statement. “Services that provide free insight into the uptake of apps are in high demand … but all of these services have only shown ranking data – until now.”

The data can tell game publishers, for example, that’s smash hit Candy Crush grew daily downloads last week, increased revenue almost ever day last week, and maintained a solid No. 2 or No. 3 ranking in one of the Apple App Store’s most important leaderboards: Top Overall (free).

App Trends - Temple Run Brave“Daily ranking data for every app worldwide in any category where it is ranked in an app store is also available, and all data can be searched by individual country,” Distimo said.

But App Trends can’t tell you exactly how many downloads or how much revenue. Or, more precisely, it won’t.

For that, you’ll have to get Distimo’s paid version, AppIQ, which provides what Distimo calls “most accurate download and revenue estimations for any app or publisher,” with daily estimates as up-to-date as two days ago. Distimo provides the data to customers like CNN, Microsoft, Amazon, and Zynga, but you’ll pay for the privilege.

How good is the data?

The majority of apps, Distimo says, are measured with an accuracy of at least 97 percent. And 95 percent of all apps are measured with an accuracy of at least 90 percent.

The data is based on Distimo’s analytics solution, which tracks three billion downloads every quarter, and competes with similar offerings from App Annie, App Data, Localytics, and others.