SimpleX¶

Best suited for: Pseudonymous online contacts; minimising account identifiers. [1] [2] [3] [4]
Avoid if…: You cannot accommodate profile, relay and local-pairing constraints. [1] [2] [3] [4]
Main strength: Relationship separation without a mandatory global identifier. [1] [2]
Main weakness: More multi-device friction; relays and notifications require care. [1] [2]
Account identifier: Local profile; relationship-specific invitations. [1] [2]
iOS: Yes, client listed in the study. [1] [2]
Android: Yes, client listed in the study. [1]
Windows: Beta; desktop-specific limits. [1] [2]
macOS: Beta; desktop-specific limits. [1] [2]
Linux: Beta; desktop-specific limits. [1] [2]
Confidence and scope: Scope-limited documentary evidence; production metadata and distributed binaries not experimentally verified. [1]

What your contact learns¶

What the contact learns: The contact receives messages and the profile you share, and can keep a copy. [1] [2]

What the provider learns: Relays see their transport data; message bodies are E2EE. Declared non-logging was not measured here. [1] [2]

What the network / ISP learns: The network sees destinations, timing and volume; Tor or a relay changes the observer. [1] [2]
Apple / Google exposure: Store, installation and push can create metadata; exact profile linkage depends on the OS and was not tested here. [1] [2]
Public law-enforcement evidence: 2025 provider claim: 12 requests with no responsive information; no independent court dossiers. [1] [2] [3]

E2EE: Double Ratchet E2EE; message padding is declared. [1] [2]
Forward secrecy: Documented Double Ratchet; versions and implementations still need verification. [1] [2]
Post-compromise security: Post-compromise recovery described by the protocol; requires an uncompromised endpoint. [1] [2]
Key verification: Unknown: not established for the version and configuration in question.

Metadata exposure: No global account; relays, queues, timing and iOS push remain exposure surfaces. [1] [2]
Global user ID: No global user ID required. [1] [2]
Username / discovery: No mandatory global username; optional public address should be avoided for compartmentalisation. [1] [2]
Push notifications: iOS push: queue and frequency data partly visible to the service; exact payload not captured. [1] [2]

IP exposure to peer: Default TURN hides IP from the peer; P2P can reveal it. [1] [2]
Relay / TURN: Always use relay; TURN sees IP and duration. [1] [2]
Calls: Documented calls; their network path must be distinguished from messaging. [1] [2]
Groups: Unknown: not established for the version and configuration in question.

Multi-device: Documented mobile–desktop pairing on the same local network; desktop beta. [1] [2]
Backups: Local profiles and history; complete version-specific backup guarantees not established here. [1] [2]

Audits: Trail of Bits 2022 and 2024 protocol review; announced 2026 review had no usable public report at the research cutoff. [1] [2] [3]
Source code and binaries: Repositories and component-specific scopes recorded in Phase 2; no current binary rebuilt bit-for-bit here. [1] [2]
Main weakness: More multi-device friction; relays and notifications require care. [1] [2]
Public law-enforcement evidence: 2025 provider claim: 12 requests with no responsive information; no independent court dossiers. [1] [2] [3]

Recommended configuration: Fresh profile, single-use invitation, no reused identity; TURN; deliberate iOS notification choice. [1] [2] [3] [4]
Remaining unknowns: Current network behaviour, distributed binaries and forensic evidence remain incomplete; check version, OS and configuration. [1] [2]

End-to-end encryption — E2EE

Participants’ devices control content keys. The transport server should not read ordinary messages. Learn more

Metadata

Data around the exchange: accounts, IP, timing, volume, devices or groups. Learn more

Pseudonymity

Use an identity different from your civil identity. It can still be linked to you. Learn more

Network anonymity

Reduce the ability to link traffic to your network address or its destination. Learn more

The detailed evidence is maintained in the French Phase 2 register. The translation is a restatement, not new evidence.