Signal vs Session vs SimpleX — Private Messaging Compared

If you’re trying to move away from WhatsApp or Telegram, three names come up again and again: Signal, Session, and SimpleX. They all claim to be private, end-to-end encrypted messaging apps, and they’re all open source.

The content encryption is genuinely good in all three. Where they really differ — and it’s a much more important difference — is metadata: who you talk to, when, and how often. That’s the thing each of them handles completely differently.

I’ve used all three, and here’s my honest take on what each one actually gets you — and what it costs you.

The Quick Overview

Signal — The best default for almost everyone. Centralised, run by a US non-profit, requires a phone number to register (usernames hide it from contacts, not from Signal).
Session — Decentralised, no phone number at all, routes messages through an onion network of community-run nodes. You get a permanent Session ID instead of a number.
SimpleX — The most radical: it has no user identifier at all — not even a random ID. You connect through one-time invitation links instead of a username or number.

Signal — The Practical Default

Signal is the one your contacts are most likely to already use, and for most people that single fact is decisive. An encrypted messenger nobody you know has installed protects nothing — it just sits on your phone looking smug.

It’s run by the Signal Foundation, a non-profit. The protocol is the double-ratchet design that WhatsApp, Google Messages and Facebook Messenger all licensed, and it’s been independently audited.

What Signal does well

E2EE by default — Every chat and call is encrypted end to end, no setting to hunt for. Group chats, voice calls, video calls, linked devices.
Audited, battle-tested — The Signal Protocol is the industry reference for forward secrecy and break-in recovery.
Minimal metadata — Sealed sender hides who sent a message from Signal’s own servers. Signal’s published transparency reports show it retains almost nothing: registration date and last connection time.
Easy for non-technical people — Install, verify your number, done. Your mum can use it.

Where Signal falls short

Phone number required — You still need one to register. Usernames (added in 2024) hide the number from the people you chat with, but not from Signal itself. Your account is tied to a number, and a number is a strong real-world identifier.
Centralised — All traffic flows through Signal’s servers, run by a US non-profit subject to US legal process. They keep little, but they’re a central point of control.

Session — Decentralised, No Phone Number

Session started as a fork of Signal that removed the phone number entirely. Instead of a number, you get a permanent Session ID — a 66-character public key. No phone number, no email, nothing personal required to sign up.

Traffic is onion-routed through the Session Network, a decentralised set of nodes run by a global community. No single node sees both ends of a conversation, and offline messages are buffered until you fetch them.

What Session does well

No phone number, no email — You can create an account with zero personal information. This is the one to pick when registering a phone number is impossible or unsafe.
Decentralised — Onion routing over many community nodes makes it far harder for any operator to see your social graph or link your IP address to your messages.
Familiar feel — It looks and works like a conventional messenger, so the learning curve is gentler than SimpleX.

Where Session falls short

No forward secrecy (yet) — Session removed perfect forward secrecy back in 2021. If a device is compromised, past messages under the same Session ID can be decrypted. A V2 protocol that restores PFS and adds post-quantum protection was announced in December 2025, but it’s still being designed.
Permanent ID — Your Session ID is stable across every conversation. It’s not linked to your legal identity, but once anything ties that ID to you, it retroactively ties everything it ever touched.
Smaller network — Fewer users, fewer contacts already on it, and some reported reliability quirks with group delivery and device sync.

SimpleX — No Identifier At All

SimpleX takes the most aggressive position in private messaging right now: it has no user identifiers whatsoever — not a phone number, not a username, not even a random account ID. It describes itself as “the first network without user IDs”.

Instead of a lookup-by-identifier, you connect to people through one-time invitation links you exchange out of band. Every contact and group lives on your device, not on a server’s database. Messages look like random noise to the relays that briefly hold them.

What SimpleX does well

Strongest metadata story — There’s no account to subpoena, no identifier appearing in two places, no social graph accumulating on a server. Whoever you talk to can’t be correlated.
Everyone runs the network — No single entity controls it. Anyone can run a SimpleX server, and the protocol passes through relays you choose.
Solid encryption — Double-ratchet end-to-end encryption with forward secrecy, plus private message routing on by default since v6.0. The protocol design was independently reviewed by Trail of Bits in 2024.

Where SimpleX falls short

Friction — No identifier means nobody can find you by username. Every new connection means exchanging a one-time link through some other channel — which is also the moment you might leak the very association you were protecting.
Harder recovery — With no server-side identity to restore from, moving devices and recovering an account is more involved than a phone-number account.
Young and smaller — It’s the newest of the three, the ecosystem is younger, and the user base is far smaller. Less battle-tested than Signal.

Which One Should You Pick?

Almost everyone: Signal. The network effect is the security property — an encrypted messenger nobody you know uses protects nothing. Turn on a username so you stop handing out your number.
Can’t register a phone number: Session. It’s the most usable option that requires nothing personal at signup.
Journalists, sources, sensitive contact relationships: SimpleX as a second messenger, alongside Signal for everyday use. Use it specifically when the fact that two people are talking is itself the sensitive part.

Whichever you pick, remember the half of the picture most people ignore: content encryption is only half the story. Your network and your habits are the other half.