SimpleX Chat

TAS Score: S3/3 — D5/5 — A3 / T2

Brief Description

Decentralized messenger with no user identifiers — no phone number, no username, no account. Uses double-ratchet encryption with pairwise connections. Self-hostable relay servers. The most private messaging option available.

Architectural Role

Client-side application layer — messaging. Relay servers (SMP) are stateless and self-hostable. No central directory or identity system.

Technical Autonomy

Works without internet (queues locally, delivers when reconnected)
Stores data locally (all messages stored on-device only)
Does not require external accounts (no identifiers at all)
Allows data export (database export/import)
Provides offline updates (APK available, F-Droid repo)

Philosophical Assessment (whose.world criteria)

Criterion	Status	Comments
Pause	✅	Stop anytime. Messages stay on device.
Exit	✅	Export database. Migrate to new device.
Recoverability	✅	Local database backup.
Visibility	✅	Fully open-source. Protocol documented and audited.
External Dependencies	✅	Can run own SMP/XFTP servers. No central dependency.

Rating key: ✅ fully meets · ⚠️ partially meets or requires configuration · ❌ does not meet

Configuration (Minimal)

Client: install from F-Droid, GitHub releases, or simplex.chat.

Self-hosted relay server:

services:
  smp-server:
    image: simplexchat/smp-server:latest
    ports:
      - "5223:5223"
    volumes:
      - ./config:/etc/opt/simplex
      - ./logs:/var/opt/simplex

Mobile Apps

Alternatives

Alternative	Autonomy	Notes
Signal	A3 / T2	More mainstream. Requires phone number. Centralized servers.
Briar	A0 / T2	P2P over Tor. Maximum security, but no export or backup by design → A0.
Element (Matrix)	A3 / T2	Federated. Richer features (rooms, bridges).

Trajectory

Sources

Website: https://simplex.chat
Documentation: https://simplex.chat/docs
Repository: https://github.com/simplex-chat/simplex-chat
Docker image: simplexchat/smp-server
Community: https://simplex.chat/contact