SimpleX Chat: The Free, Open Source Messenger With No Phone Number, No User IDs, and Post-Quantum Encryption (2026 Guide)

Every mainstream messaging app wants something from you before you can send a single text. WhatsApp demands your phone number. Telegram wants a phone number too. Signal, despite its excellent encryption, still requires a phone number to register. All of them run on centralized servers that log metadata: who you talk to, when, and how often. That metadata is enough to map your entire social graph without ever reading a single message.

SimpleX Chat is a free, open source messenger that fixes this by completely eliminating user identifiers. There are no phone numbers, no emails, no global user IDs, and no accounts. It routes messages through decentralized, unidirectional queues using double-ratchet encryption and post-quantum key exchanges by default. The servers act as dumb pipes that relay encrypted traffic with zero knowledge of who is communicating with whom.

In this guide, you'll learn what SimpleX Chat is, who it's for, and how to install it on desktop and mobile, create your first profile, and connect with contacts securely.

What is SimpleX Chat?

SimpleX Chat is an open source messaging platform that fundamentally reimagines secure communication by removing all user identifiers from the protocol. Unlike traditional messengers that rely on phone numbers, emails, or global user IDs to route messages, SimpleX uses decentralized, unidirectional message queues. Each conversation uses separate sending and receiving queues, and the relay servers that pass the traffic have no way to link a sender to a recipient. The servers are genuinely dumb pipes.

The encryption stack is serious. SimpleX uses double-ratchet encryption for forward secrecy on every message, and it includes post-quantum key exchanges by default. This means your conversations are protected not just against current surveillance techniques but against future quantum computing attacks that could break classical encryption retroactively. Few messengers ship post-quantum cryptography enabled out of the box.

Because there are no accounts, connections between users are established through single-use QR codes or one-time invite links. You can generate a random alias and profile for every single contact or group using Incognito Mode, which prevents anyone from linking your identity across different conversations. The app also has native support for routing all traffic through the Tor network, completely obfuscating your IP address. For developers and power users, there is a full CLI daemon that can run on headless servers and be scripted programmatically.

Who is it for?

Privacy advocates: Users who want to message friends and family without handing over their phone number or metadata to a centralized corporate server.
Journalists and activists: Individuals operating in hostile or highly surveilled environments who need reliable, untraceable communication that leaves no metadata trail.
Security teams: Organizations testing or implementing zero-trust environments and needing an out-of-band, high-security communication channel for sensitive operations.
Tech enthusiasts: Open source fans who enjoy self-hosting relay servers, running the CLI daemon on headless machines, or interacting with the app via its terminal interface.

What makes SimpleX different from Signal and WhatsApp?

Zero identifiers: There are no user IDs, phone numbers, emails, or accounts of any kind. Connections are made strictly via single-use QR codes or one-time invite links, so no central authority can map your social graph.
Unidirectional message queues: The app uses separate paths for sending and receiving messages, making traffic correlation attacks exceptionally difficult even for an adversary monitoring the network.
Post-quantum encryption by default: SimpleX uses advanced cryptography designed to resist decryption by future quantum computers, enabled automatically without any configuration required.
Incognito mode: Allows you to generate a random alias and profile for every single chat group or contact, preventing linkage across different conversations and groups.
Tor and Tails compatibility: Native support for routing all traffic through the Tor network to completely obfuscate IP addresses, and it runs on Tails OS for ephemeral, amnesic sessions.
Free and open source: The entire client and server stack is free and open source under the AGPL-3.0 license. You can self-host your own relay servers for complete infrastructure control.

What you need before you start

Before installing SimpleX Chat, make sure you have the following:

Operating system: Linux (via Flatpak or AppImage), macOS, Windows, Android, or iOS. All platforms are officially supported.
Hardware: Any modern desktop, laptop, or mobile device. There are no special hardware requirements.
Network: A standard internet connection. For enhanced privacy, the app can be configured to route all traffic exclusively through Tor.
Package manager (Linux desktop): Flatpak for the graphical client, or terminal access for the CLI daemon binary.
Mobile app store: Google Play Store, F-Droid, or Apple App Store for mobile installation.

Step-by-step installation

Step 1: Install the SimpleX app

SimpleX is available on mobile app stores and desktop. The easiest way to install the graphical client on Linux is via Flatpak:

flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
flatpak install flathub chat.simplex.simplex

On macOS and Windows, download the installer directly from the SimpleX website. On Android, install from Google Play or F-Droid. On iOS, search for SimpleX Chat in the App Store.

Alternatively, if you prefer running the CLI daemon for scripting or headless servers, grab the binary directly from GitHub:

curl -L https://github.com/simplex-chat/simplex-chat/releases/latest/download/simplex-chat-ubuntu-22_04-x86_64 -o simplex-chat
chmod +x simplex-chat
./simplex-chat -p 5225

Step 2: Create your first profile

Launch the application. You will be prompted to create a profile. Because there are no central servers holding your data, everything is generated locally on your device:

Enter a display name. This is stored locally and only shared with people you explicitly connect with.
Choose whether to enable Incognito Mode for maximum privacy. This generates a random alias per contact.
Click Create. Your profile and encryption keys are generated entirely on your device.

Step 3: Secure your local database

SimpleX stores all your chats, encryption keys, and connection data locally on your device. You will be asked to set a passphrase to encrypt this local database:

If you already use full-disk encryption like LUKS on Linux or FileVault on macOS and trust it, you can opt to use a random passphrase generated by the app.
Otherwise, enter a strong, memorable passphrase that you will not lose. There is no password recovery because there is no central server.

Step 4: Connect with contacts

Because you have no username or phone number, you must create a connection link to chat with someone:

Click the New Chat button in the app.
Select Create one-time invitation link.
Share this link or let your contact scan the generated QR code through a secure channel.

Once they accept, a secure end-to-end encrypted connection is established using decentralized relay servers. The one-time link expires after a single use, so it cannot be reused or intercepted.

Common errors and how to fix them

Error	What it means	How to fix it
INTERNAL SEUniqueID Error	Happens when trying to send media files after importing a database backup to a new machine.	Often caused by permission mismatches in the imported directory. Ensure the SimpleX app has full read and write permissions to the restored database folder.
Crash on Linux launch	The graphical client crashes immediately upon opening on certain Linux distributions.	Typically an issue with bitmap PCF fonts. Disable bitmap fonts in your system font settings or install standard TrueType (TTF) fonts instead.
Notification flood on startup	Upon starting the app, you receive a massive spam of notifications from past offline messages.	Adjust your notification settings within the app. Opt for background sync where permitted rather than instant push alerts for every queued message.
Cannot connect to relay / messages stuck	The default relay server is down or unreachable from your network.	Change your configured relay servers in Settings to a different public relay, or self-host your own SimpleX SMP server for full control.

SimpleX vs traditional cloud messengers

Feature	SimpleX (open source)	Traditional messengers (WhatsApp, Telegram)
Pricing	100% free, donation supported	Free, funded by data and ads
Account requirement	None, no phone number, email, or ID	Requires phone number to register
Metadata protection	Total, decentralized routing with zero correlation	Minimal, servers log who you talk to and when
Network structure	Decentralized, user-chosen relays	Centralized corporate servers
Post-quantum encryption	Enabled by default	Not available
Best for	People who need absolute privacy and anonymity	People who want convenience and ubiquity

Bottom line: SimpleX Chat is arguably the most private messaging platform available today. By completely stripping away user identifiers and using decentralized relay nodes with post-quantum encryption, it trades a slightly steeper learning curve for absolute anonymity. While WhatsApp and Telegram are free to use, you pay with your metadata and phone number. SimpleX costs nothing, requires no account, and lets you self-host the entire infrastructure. If you want a free, open source alternative to Signal that goes further on privacy, this is the best option available.

3 alternatives worth checking out

Signal (signal.org): The gold standard for end-to-end encrypted messaging. It is incredibly user-friendly and features audited, post-quantum cryptography, but it relies on centralized servers and still requires a phone number to register. If you want maximum privacy with zero friction for non-technical contacts, Signal is the easiest recommendation.
Session (getsession.org): An open source messenger that requires no phone number and relies on an onion-routed network to obscure IP addresses and metadata. It is easier to set up than SimpleX but lacks forward secrecy in its current implementation, making it a solid middle ground between convenience and privacy.
Threema (threema.ch): A paid, highly polished Swiss messaging app that requires no phone number. It uses centralized servers for reliability but minimizes data collection and is fully GDPR compliant. If you want a privacy-first messenger with a more traditional UX and are willing to pay a one-time fee, Threema is worth considering.

Found this guide useful? Check out more free alternatives and open source projects on Sudo Scout.