Summary of the findings

Main conclusions

1. There is no universal winner. The answer changes with the adversary, platform, identity model and need for calls or groups.
2. E2EE is not anonymity. A service may be unable to read message content while still observing account, IP, timing or traffic metadata.
3. SimpleX is the strongest practical starting point for separating a new pseudonymous identity from a contact met on Discord. It does not require a phone number, email address or global user identifier.
4. Signal becomes much stronger in a pseudonymous configuration. With number visibility and discovery set to Nobody, a fresh username and a neutral profile, the other participant does not need to receive the phone number. Signal still requires a number at registration.
5. For iPhone + PC, Signal is the most practical secure option in this study. SimpleX, Olvid and Threema are alternatives with different multi-device trade-offs.
6. Olvid and Threema are good choices when the goal is not to give a phone number to the contact, but they are not network-anonymity systems.
7. Session is temporarily downgraded for high-assurance use because of the 2026 WOOT research on Session Protocol V1 and the unresolved status of fixes/retesting in this report.
8. Cwtch and Briar are specialised tools. Their Tor-oriented designs are relevant to some network threats, but there is no official iOS client established here.
9. Calls are a separate network path. P2P may reveal IP addresses to the peer; TURN hides the peer IP but exposes metadata to the relay.
10. No messenger in this study demonstrates general resistance to a global passive adversary. Low-latency onion routing does not remove timing and volume correlation risks.
11. Endpoints dominate after compromise. An unlocked phone, spyware, notification database or malicious correspondent can expose plaintext regardless of the transport protocol.
12. Public legal evidence is uneven. Signal, Threema, Discord and Wire have concrete public examples of account metadata or messages being produced in specific cases; absence of a public case for another service is not proof that no disclosure exists.
13. Open source is not the same thing as a verified distributed binary. Version 1.0 did not rebuild every current APK, IPA or desktop package bit-for-bit.

Practical starting points

Situation	First options to examine
Everyday secure messaging	First options to examineSignal
Pseudonymous contact met online	First options to examineSimpleX; Signal with hardened privacy settings
No phone number shared with the peer	First options to examineSimpleX, Threema, Olvid
Tor-oriented messaging	First options to examineCwtch, Briar
Teams / self-hosted collaboration	First options to examineMatrix / Element
Mainstream adoption	First options to examineSignal; WhatsApp when adoption is the overriding constraint

Read the quick guide before the full comparison if you want the shortest path to a decision.