Complex sentence: Whisper is a proprietary iOS and Android mobile app available without charge, which allows users to post and share photo and video messages anonymously, although this claim has been challenged with privacy concerns over Whisper's handling of user data.
Split into simpler sentences: Whisper is a proprietary iOS and Android mobile app available without charge. It is a form of anonymous social media, allowing users to post and share photo and video messages anonymously, although this claim has been challenged with privacy concerns over Whisper's handling of user data.