Why it's similar
WhatsApp shares Signal's end-to-end encryption and full messaging suite, texts, voice and video calls, groups, and media, used by a massive global audience. Both protect message content by default. At 4.69 across 17,823,954 ratings it dwarfs every other pick.
How it differs
WhatsApp's encryption protects content but it collects more metadata and is owned by Meta, where Signal is privacy-first and nonprofit. Reviewers also report aggressive spam bans and lost chats behind encryption passwords. Its huge user base is the draw, so it suits reaching people who already use it over Signal's stricter privacy.
