The company also cautioned that it may collect information like device identifiers, cookies, IP addresses and geographic locations and time zones, which is information that in some cases has been defined under the Children's Online Privacy Protection Act (COPPA) as personal information.
An "Ask to Buy" feature will allow parents to approve apps or in-app purchases by children.
"We're going to make sure you get updates here about privacy at Apple at least once a year and whenever there are significant changes to our policies," Cook wrote in the letter.
Cook also addressed a key concern of many users about tech companies sharing data with governments, an issue that came up after former U.S. National Security Agency contractor Edward Snowden leaked documents that telecommunications and Internet companies were providing user data to the agency.
"I want to be absolutely clear that we have never worked with any government agency from any country to create a backdoor in any of our products or services," Cook said. "We have also never allowed access to our servers." This has been a stand taken by other Internet companies as well.
Apple said it didn't have a way to decrypt iMessage and FaceTime data when it's in transit between devices. "So unlike other companies' messaging services, Apple doesn't scan your communications, and we wouldn't be able to comply with a wiretap order even if we wanted to," it said on its website.
The company, however, complies with requests for information if it is accompanied by valid legal process. The most common requests it receives for information come from law enforcement in the form of either a device request mainly for helping locate a stolen device or an account request usually asking for information on an iTunes or iCloud account.
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