SimpleX
SimpleX is a private and encrypted messenger that operates without any user identifiers — not even random usernames or phone numbers. Instead of using a user ID system, SimpleX creates a network of message queues where each conversation uses a unique pair of cryptographic keys. There is no central directory, no global profile, and no way to look up a user. You connect via one-time invitation links or QR codes, which establish a direct encrypted channel between two parties.
Key Features
- No user identifiers — Unlike every other messaging platform, SimpleX has no usernames, phone numbers, or even random IDs. Your identity is purely cryptographic, tied to each conversation independently.
- End-to-end encryption by default — All messages are encrypted using the Double Ratchet algorithm (the same protocol used by Signal). The encryption is not optional — it is always on.
- Decentralised message relay — Messages pass through a network of relay servers (SMP servers) that have no knowledge of sender or recipient identities. You can run your own relay server for self-hosted setups.
- One-time invitation links — Share a one-time QR code or link to start a conversation. After the first connection, the link is useless, preventing replay attacks and unwanted contact attempts.
- Multi-device support — Use SimpleX on multiple devices simultaneously. Each device gets its own cryptographic identity tied to your account, and messages are synced securely.
- Minimal metadata — Because there are no user identifiers, the relay network cannot determine who is talking to whom, how many contacts you have, or any usage patterns. Metadata collection is effectively impossible.
- Voice messages and file sharing — Send voice recordings, images, documents, and files with the same privacy guarantees as text messages. All content is end-to-end encrypted.
- Open source and auditable — The entire stack (client apps, relay server, protocol) is open source under AGPLv3. The protocol has been independently audited by Trail of Bits.
Why Use SimpleX?
SimpleX is for users who want the highest possible privacy in messaging — the kind that doesn’t just encrypt message content but eliminates metadata entirely. For journalists, activists, whistleblowers, or anyone who needs deniable and untraceable communication, SimpleX offers a fundamentally different approach to messaging security. It is also excellent for privacy enthusiasts who want to self-host their messaging infrastructure without managing user accounts.
Use Cases
- High-security communications where metadata leakage (who talks to whom, when) is more sensitive than message content
- Journalists and sources needing deniable contact channels that can’t be traced back to either party
- Privacy-focused individuals who want to avoid the data collection and profiling present in mainstream messaging platforms
- Self-hosters who want to run their own relay servers for complete control over message routing infrastructure
Platform
Linux · macOS · Windows · Android · iOS
Licence
GNU Affero General Public License v3