Facebook co-founder, Chairman and CEO Mark Zuckerberg testifies before the House Energy and Commerce Committee in the Rayburn House Office Building on Capitol Hill April 11, 2018 in Washington, DC.

In 2013, Facebook bought an Israeli app developer called Onavo, whose service helps consumer protect their mobile data while browsing. Now, the company has told legislators that it does not connect data from Ovavo to individual users' Facebook profiles, while acknowledging it does use Onavo data to see what people are doing in other products and improve its own products accordingly.

Congress asked Facebook about Onavo in written questioning following CEO Mark Zuckerberg's congressional testimony in April, which came in response to the Cambridge Analytica data-sharing scandal. On Monday, the company submitted hundreds of pages of answers to those questions.

Legislators wanted to know if Facebook uses traffic data collected from Onavo to "monitor the adoption or popularity of non-Facebook applications." They also asked whether Facebook has used Onavo data in deciding whether to acquire companies or develop a particular product, and whether it links Onavo traffic information to profile data from its core services, "including for analytic purposes."

In its response to Congress, Facebook said it "does not use Onavo data for Facebook product uses, nor does it append any Onavo data or data about individuals' app usage to Facebook accounts."

However, while personal information isn't used, Facebook does look at Onavo's broad data sets to see what types of products are popular and how customers are using them.

The company said it tells Onavo customers on the first screen they see that the product is owned by Facebook and that Facebook uses what it learns to help improve its offerings.