Start private conversations without leaving contact lists on servers
If you want to hide who you talk to and when, this chat app provides that level of privacy. It operates on a network with no user numbers or names, protecting not just message content but also who is connected to whom. You can start a trace-free private conversation by installing the app and sharing a link with a friend.
Connection without identifiers
Existing messengers assign phone numbers or random IDs to distinguish users, but SimpleX removes these entirely. Instead, it establishes connections by sharing one-time invitation links or temporary addresses, ensuring that the other party's identity or contact list is not stored on the server. Each conversation uses an independent message queue, so there is no common metadata between conversations with different people. This makes it difficult for observers to infer a user's social network.
Security structure and encryption
Messages are end-to-end encrypted using the Double Ratchet algorithm, with an additional encryption layer applied via NaCl cryptobox. Recent updates have also introduced a key exchange method to prepare for quantum computer attacks. Servers store messages only temporarily and delete them immediately upon receipt by the recipient. Additionally, to protect IP addresses, personal message routing is enabled by default from v6.0 onwards, and access via the Tor network is supported.
App installation and usage
Mobile apps are available for Android and iOS, while a terminal-based CLI app is available for Linux, MacOS, and Windows. The mobile app can be installed from Google Play, APK, or the App Store, and iOS users can preview the latest features via TestFlight. The terminal app can be installed easily with the curl command and run by executing the simplex-chat command. Developers can also build chat bots or services using the Haskell library or TypeScript client.
Current status and verification
The platform has been consistently updated since the mobile app launch in March 2022 and underwent an encryption protocol review by Trail of Bits in July 2024. However, as it is still an early-stage platform, it may contain bugs or missing features. The default server is operated on a best-effort basis and has maintained an uptime of over 99.9%, but no official SLA is guaranteed. Users should determine if the security level suits their use case, and Tor usage is recommended if IP address protection is a priority.
