Signal is described as 'An encrypted messaging app focused on privacy, supporting texts, calls, photos, videos, files, and group chats, with no ads or trackers' and is a leading instant messenger in the social & communications category. There are more than 100 alternatives to Signal for a variety of platforms, including Android, iPhone, Windows, Linux and Mac apps. The best Signal alternative is Element. It's not free, so if you're looking for a free alternative, you could try Element or Tox. Other great apps like Signal are Matrix, Discord, Telegram and Threema.
Decentralized messaging app enabling secure peer-to-peer communication over Bluetooth mesh networks with end-to-end encryption, channel-based group chats, store & forward delivery, automatic peer discovery, no accounts or phone numbers, and privacy safeguards.
Exchange messages without SMS fees using this app for iPhone, Android and desktop, featuring group chats, multimedia sharing, and video calls. The app requires an internet connection and the latest version for optimal functionality.
WhatsApp is owned by facebook. Google "Facebook Privacy" and you'll see why this is one of the worst alternatives.
Also end-to-end encrypted by default.
Provides a chat experience over email, with all messages and contacts stored on user devices, open source code, group media support, and compatibility with any provider. No central servers, no tracking, works without SIM, and can be used by anyone just via email.
The concept of DeltaChat is so simple and brilliant! Secure chat on top of an infrastructure that is already there: Email and the IMAP-protocol.
Provides secure end-to-end encrypted video calls with privacy features such as background blur, noise reduction, and meeting locks, supports up to 50 free participants, guest links, ad-free use, seamless calendar integration, and multi-device access.
Threaded group conversations combine live and asynchronous messaging, separating topics for organized collaboration, supporting open-source, cloud, and self-hosted deployments, secure communication with encryption, and multi-platform access for diverse teams.
Zulip is the only other open source, secure option in the list of alternatives on this site.
It is the brand new, and fastest ever, Matrix client. It is for personal and community use, and will support enterprise functionality later this year.
Open source, decentralized platform enabling encrypted chat, secure voice and video calls, anonymous file sharing with swarming, censorship-resistant forums, channels, link sharing, and offline messaging. Uses OpenPGP and OpenSSL for robust privacy and security.
Retroshare has all the advantages of Signal and none of its disadvantages.
Conversations is a privacy focused, open source XMPP Texting [Jabber] client for Android 4.0+ smart phones with wife-approved easy encryption [OTR, OMEMO, or GPG].
Uses OMEMO, OTR, and/or GPG encryption and is decentralized. Also it's open source.
Has End-to-End encryption by default. Is decentral/federated so not to block or shutdown.
From my point of view Conversations is the most user-friendly XMPP client for Android. It also does not require a phone number, is decentralized and looks just great.
Keybase is a new and free security app for mobile phones and computers. For the geeks among us: it's open source and powered by public-key cryptography.
It doesn't need telephone number
Encrypted messenger supporting multi-platform access, unlimited group and private chats, file and voice message sharing, decentralized operation, open-source code, custom themes including dark mode, advanced moderation, push notifications, and no advertisements.
Offers secure messaging with end-to-end encryption, unlimited free calls, group chats for up to 250 members, rich media sharing, emoji reactions, AR lenses, self-destruct messages, affordable international calls, community channels, and robust privacy across devices.
Prioprietary bloat, do not use.
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WhatsApp is not Free Software and is not focused on privacy. Difficult to use in Usecases which demand high control of the Software and a verifiable Data-protection