What is End-to-end encryption?

End-to-end encryption means a message is scrambled on the sending device and only readable on the receiving device, so the service in the middle cannot open it. Providers describe scope differently, and that wording matters. Briar end-to-end encrypts all communication between devices, and each user's contact list stays encrypted on her own device. Abine, Inc. states no end-to-end encryption, only encryption at rest and in transit. Apple Hide My Email relays and forwards alias mail, and none of that mail is end-to-end encrypted.