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SimpleX Chat
SimpleX Chat is an open-source, decentralized messaging platform designed for privacy and security. Its core architectural principle is the complete absence of user identifiers, meaning it does not use phone numbers, usernames, or even random numbers to identify users on the network. This design aims to protect not only message content with end-to-end encryption but also metadata about who is communicating.[1][2]
Overview
SimpleX Chat was developed to provide a communication platform where users have full ownership and control over their identity, contacts, and data, free from centralized oversight. The project's mission is to offer a high degree of metadata protection, making it difficult for servers or network observers to determine the social graph of its users. Communications are routed through a decentralized network of SimpleX Messaging Protocol (SMP) servers, and users can host their own servers for greater autonomy. As of October 2026, the SimpleX homepage reports 3 million downloads and 600,000 monthly users. The project has expanded from a private messenger toward a broader platform that includes privacy-preserving public channels and business and community functions.[1]
The platform operates on a custom-built protocol stack designed to minimize metadata exposure. Unlike conventional federated systems, SimpleX relays do not have a shared user address space, and each connection between users is isolated. While the project is supported by a for-profit company and has received venture capital funding, its developers have stated a long-term vision for protocol governance to be managed by non-profit entities to ensure its alignment with community interests. The project has been endorsed by privacy-focused organizations like Privacy Guides and Whonix and has gained public recognition from figures in the technology space, including Ethereum founder Vitalik Buterin.[4][5]
History
Development of SimpleX began around 2020. The first prototype of the SimpleX Messaging Server was announced in October 2020, followed by a terminal-based chat application in May 2021. The first public version of the mobile apps for iOS and Android, SimpleX Chat v1, was released in March 2022.[6][3]
Significant milestones in the platform's development include:
- July 2022 (v3.0): Introduction of end-to-end encrypted audio and video calls.
- August 2022 (v3.1): Added support for routing traffic through Tor via a SOCKS proxy and introduced secret chat groups.
- September 2022 (v3.2): Launched "Incognito Mode," allowing users to create a new random profile name for each new contact.
- November 2022 (v4.2): Published a security assessment conducted by the firm Trail of Bits.
- February 2023 (v4.5): Introduced multiple, separate chat profiles within a single app.
- March 2024 (v5.6): Implemented quantum-resistant encryption as a beta feature, using a hybrid post-quantum key exchange mechanism alongside the Double Ratchet algorithm.
- June 2024 (v5.8): Introduced Private Message Routing to hide user IP addresses from destination servers.
- August 2024 (v6.0): Announced an investment from Jack Dorsey and the firm Asymmetric. Private Message Routing became the default setting for all new connections.
- October 2024 (v6.1): Published a new cryptographic design review by Trail of Bits.
- December 2024 (v6.2): Announced a partnership with Flux to include Flux-operated servers in the app to enhance decentralization and privacy.
- July 2025 (v6.4.1): Introduced community protection features, such as the ability for group administrators to review new members before they can join.
- April 30, 2026 (v6.5): Introduced the first beta of SimpleX Channels and announced plans for a SimpleX Network Consortium.[9]
- July 2026 (v7.0): Introduced beta public names for channels and businesses, contributor roles for channels, channel relay self-hosting, and other channel improvements.[10]
- July 7, 2026: Published the Community Credits whitepaper, describing a proposed privacy-preserving payment design for network capacity.[11]
- August 20, 2026: Launched equity crowdfunding on Wefunder.[12]
- September 2026 (v7.1 beta): Introduced anonymous Supporter Badges.[13]
- October 20, 2026 (v7.1.0-beta.7): Added Markdown messages and file viewing, call reconnection after brief network interruptions, warnings before calls without E2EE, Android secure-chip storage for database passphrases where available, and badge-enabled larger and longer file transfers. These were beta-release features.[14]
The project's roadmap has included goals for scaling the network for large communities. Its current roadmap places testing of Community Credits in 2026–27 and lists June 2027 for launching the credits system.[15]
Architecture and Technology
SimpleX is built on a custom protocol stack designed specifically to operate without user identifiers and to minimize metadata leakage.
No User Identifiers
The foundational principle of SimpleX is the absence of any persistent, globally unique user IDs. Unlike other secure messengers that rely on phone numbers (Signal) or public key-based IDs (Session), SimpleX isolates every connection. A user's profile, contact list, and group memberships exist only on their local device. When connecting with a contact, the app creates a new, distinct set of identifiers for that specific relationship. This makes it computationally difficult for a network-level adversary to build a social graph of who is communicating with whom.[4][2]
Network and Protocols
The platform operates on a decentralized network of servers running its custom protocols.
SimpleX Messaging Protocol (SMP) and SimpleXMQ
SimpleX's network functionality is based on two key protocols:
- SimpleXMQ (SimpleX Message Queue): This is the low-level message queue protocol that defines how messages are passed through unidirectional (simplex) message queues. The reference implementation, also called SimpleXMQ, is written in Haskell and serves as the message broker for the network.[7]
- SMP (SimpleX Messaging Protocol): Built on top of SimpleXMQ, SMP is a client-server protocol that manages communication and the creation of message queues. A full bidirectional conversation between two users consists of two separate, unidirectional SMP queues—one for sending and one for receiving.[7]
SMP servers act as relays. They receive encrypted messages from a sender and place them in the correct anonymous queue, where they are later retrieved by the recipient. The server only sees a series of isolated message deliveries to opaque queue identifiers and cannot link the sender and receiver. Users can run their own SMP servers for maximum control and privacy.[2]
Private Message Routing
To protect a user's IP address from their contact's server, SimpleX implements a system called Private Message Routing. Enabled by default since version 6.0, it uses a two-hop packet routing mechanism. A user's client encrypts the message for the destination server and then wraps it in another layer of encryption for a forwarding server. The forwarding server relays the packet to the destination server without knowing the final recipient's queue ID or the message content. This packet-based routing approach provides per-packet anonymity, preventing a destination server from linking multiple messages to the same user.[4]
Encryption
SimpleX employs multiple layers of encryption to secure communications.
- End-to-End Encryption (E2EE): All one-to-one and group messages are E2E encrypted using the Signal Double Ratchet algorithm, which provides forward secrecy and post-compromise security.
- Post-Quantum Resistance: Since version 5.6, the platform incorporates a hybrid post-quantum key exchange using CRYSTALS-Kyber. This runs in parallel with the classic key exchange to protect conversations against future attacks from quantum computers.
- Transport Encryption: All communication between clients and servers is secured with TLS.[4]
- Local Encryption: The app also supports the encryption of the local chat database and media files stored on the user's device.[6]
File and Call Protocols
- SimpleX File Transfer Protocol (XFTP): For sending files, SimpleX uses a proprietary protocol designed to minimize metadata leakage. Files are temporarily stored on XFTP servers, and users can host their own.
- Voice and Video Calls: Calls are E2EE and use WebRTC technology. Users can configure their own STUN/TURN servers for routing calls, offering an additional layer of privacy.[2]
Features
SimpleX Chat is available on iOS, Android (via Google Play, F-Droid, and direct APK), Windows, macOS, and Linux.[1]
- Communication: The app supports direct and secret group messaging, E2E encrypted audio/video calls, voice messages, message reactions, editing, and disappearing messages.[6]
- Profiles and Identity: Users can create multiple, isolated chat profiles within the app to separate different social contexts. An "Incognito Mode" generates a new random name for each new connection, further obscuring the user's main profile.[4]
- Connections: Users connect by sharing one-time invitation links or QR codes. Reusable SimpleX addresses can also be created for sharing publicly.[2]
- Message Delivery: The app uses a two-checkmark system to indicate message delivery: one check for delivery to the recipient's server queue and two checks for delivery to their device. The platform does not implement "read receipts," which the developers consider an "anti-feature" that creates social pressure.[4]
- Multi-Device Support: SimpleX does not support using the same profile seamlessly across multiple devices, as the developers view existing solutions as a security compromise. However, a mobile app can be linked to a desktop client on the same local network, which then acts as a remote for the mobile device.[4]
- Tor Integration: The app supports using Tor for network transport by configuring a SOCKS proxy (e.g., via Orbot). Tor is not bundled directly with the application.[4]
SimpleX Channels
Introduced in beta in v6.5, SimpleX Channels are a public publishing feature distinct from private end-to-end encrypted chats: channel content is visible to relay operators. Channel owners’ and subscribers’ identities and participation are designed to remain private from relay operators, one another, and the network. Each channel uses multiple relays for availability, and owners hold their own channel keys. Channels can be listed in the SimpleX Directory; supported functions include channel webpages, contributors, and self-hosted relays.[9][10]
Optional public names for channels and businesses are based on the SimpleX Name Service on Ethereum, with ownership controlled by the owner's wallet key. Test names are available; public name sales are planned for December 12, 2026, according to the project roadmap.[16]
Supporter Badges
Supporter Badges are available in the v7.1 beta. The badge is an anonymous credential stored in the local profile, using unlinkable zero-knowledge proofs that are not tied to user accounts. Supporter Badges allow files up to 2GB and seven-day file retention; Legend Badges allow files up to 5GB and 21-day retention. The default limits are 1GB and two days. As a beta feature, Supporter Badges are not a stable general release.[13][14]
Funding and Business Model
SimpleX Chat is developed by SimpleX Chat, Inc. and is funded through a combination of community donations and venture capital. In August 2024, the project announced an investment from Jack Dorsey and Asymmetric Capital Partners. On August 20, 2026, SimpleX Chat launched equity crowdfunding on Wefunder, allowing community members and the public to invest in the company.[6][12] The team has justified the use of VC funding as a practical necessity to compete with large, well-funded technology companies and to finance the research and development required.[4]
The project's business direction is to keep private direct messaging free while developing revenue products that include public names, business messaging, and additional infrastructure and capacity for large channels. The project has also described Community Credits as a proposed way to pay for network capacity.[15]
Community Credits
Community Credits is the current name for a proposed payment system for SimpleX Network capacity; earlier project material referred to the plan as Community Vouchers. The July 7, 2026 whitepaper describes a closed-loop, privacy-preserving prepaid design. Credits are non-transferable, expire, and are backed one-for-one by stablecoin held in a non-custodial smart contract. They are bought openly, assigned to communities, and redeemed to registered operators using zero-knowledge proofs intended to make purchases, assignments, and individual redemptions unlinkable.[11]
The proposed architecture targets EVM-compatible chains, but the project page says that it is still evaluating which chains to use. Operators are proposed to receive up to 70% of infrastructure payments, with the remainder supporting development and governance. The current roadmap places a test version in 2026–27 and lists June 2027 for launching Community Credits.[11][15]
Earlier preliminary material estimated monthly pricing at 10 for a community of 5,000 active users, with a free tier for smaller groups. This was an earlier estimate, not current pricing.[8]
Security, Privacy, and Advocacy
Privacy and security are central to the SimpleX project. The platform has undergone and published multiple third-party security audits by the firm Trail of Bits in 2022 and 2024. The project also reported a Trail of Bits audit in 2026; in August 2026, it described the report as pending publication. In April 2024, the project published legally binding Transparency Reports, affirming its commitment to its privacy claims.[6][12][1]
SimpleX Chat is a vocal advocate for digital privacy. In November 2025, the project took a strong stance against the EU's "Chat Control" legislation, arguing that its true purpose was to enable mass surveillance for training AI models. This advocacy aligns with endorsements the project has received from prominent figures in the privacy space. On November 26, 2025, Ethereum founder Vitalik Buterin mentioned SimpleX as one of two messaging apps "pushing forward" important next steps for privacy, specifically "permissionless account creation" and "metadata privacy."[5]
Team
Evgeny Poberezkin founded SimpleX Chat and created Ajv, a widely used JavaScript library for data validation.[3]
In April 2026, the project announced a proposal for a SimpleX Network Foundation and a consortium agreement with SimpleX Chat, Inc. By July 2026, SimpleX described the SimpleX Network Consortium as established between the non-profit foundation and SimpleX Chat, Inc. for protocol licensing and governance, as a structural step toward separating protocol stewardship from the commercial company.[9][16]
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