Skip to main content

Documentation Index

Fetch the complete documentation index at: https://mintlify.com/simplex-chat/simplex-chat/llms.txt

Use this file to discover all available pages before exploring further.

SMP servers are simple, stateless message relay servers that sit between SimpleX clients. They hold encrypted messages only until a recipient picks them up — and then immediately delete them. Crucially, an SMP server never knows who is communicating with whom: it only ever sees opaque queue IDs and ciphertext it cannot read.

​
What SMP servers do

  • Accept inbound encrypted messages addressed to a queue ID
  • Store those messages temporarily until the recipient retrieves them
  • Delete messages immediately and permanently after delivery
  • Authorize incoming messages using Ed448 keys — without ever identifying the user behind them
  • Optionally expose a .onion address so Tor users can connect without touching the clearnet

​
What SMP servers do NOT do

  • Store user identities, display names, or any profile data
  • Know who is sending to whom — the server only sees anonymous queue IDs, never the real participants
  • Read message content — all payloads are end-to-end encrypted by clients before they reach the server
  • Persist logs of delivered messages — once a message is picked up it is gone

​
Pre-configured servers

SimpleX mobile and desktop apps come pre-configured with three relay servers operated by SimpleX Chat Ltd:
  • smp11.simplex.im
  • smp12.simplex.im
  • smp14.simplex.im
These servers are used for new contacts by default. You can add your own server alongside them or replace them entirely — existing contacts are not automatically moved, but you can migrate each one individually using the Change receiving address option in the contact’s information page.

​
Why self-host?

Full independence

No reliance on simplex.chat infrastructure. Your messages never touch servers you don’t control.

Private relay

Only the contacts you invite use your server. You decide who can create messaging queues.

Custom retention

Configure message expiry, storage quotas, and exactly how long undelivered messages are held.

Onion address

Add a .onion address so Tor-only users can connect without exposing their IP to your server.

​
Requirements

Before you start, make sure you have the following:
  • A VPS or dedicated server running a Linux distribution (Ubuntu is recommended)
  • A domain name pointed at your server with A (and optionally AAAA) records — for example, smp.example.com
  • Ports 443 and 5223 open in your firewall (port 80 is also needed for Let’s Encrypt certificate issuance)
  • Basic Linux command-line knowledge

Build docs developers (and LLMs) love

Get started for freeTalk to us