"Signal messages, pictures, files, and other contents are stored locally on your device. These contents are readable by the open source Signal clients. Because everything in Signal is end-to-end encrypted, the Signal service does not have access to any of this data. There are several community-developed open source utilities that are capable of parsing locally stored Signal content. Android users can also help us test a new backup feature that makes it possible to move your local Signal data between devices (Signal Settings > Chats and media > Chat backups). [...] You can permanently disable your phone number from being recognized as a Signal user by unregistering your phone number here. You will need access to this phone number to verify and complete this action. [...] Signal does not store any contact information under any circumstances. That information resides solely on your device."