How Colitu Adaptive Connect works

#4 protocol families, 5 connection modes

Every Colitu server offers all five connection modes at the same time. They come from four protocol families: Hysteria2, VLESS (Reality and XHTTP), Trojan and Shadowsocks 2022. The Windows, Android (including TV), iOS and Linux apps all support all five.

#How is the server chosen?

If you picked a location, Colitu uses it and never moves you elsewhere on its own. A choice you make by hand is never switched.

With Fastest server (automatic mode) the app chooses the server. The order is:

1. 1
   The server that worked last time on the network you are on now comes first. This is remembered for 24 hours.
2. 2
   Otherwise the server with the lowest measured ping wins. Pings older than 10 minutes, or measured on another network, don't count.
3. 3
   Servers in other countries come before servers in your own country, and nearer countries before distant ones. This also decides the order when there is no ping yet.
4. 4
   A server that didn't answer the ping goes to the end of the list.
5. 5
   A server that failed on this network in the last 30 minutes goes last.

Recommended in the server list always shows the server automatic mode would connect to.

A server can answer the ping and still carry no traffic on some networks. That is why ping is only a hint; real traffic has the last word.

How is the list ordered?

The Colitu panel orders the server list using your country and your internet provider's network. Both are worked out from the IP address of that one request only, and nothing is stored. When the request arrives through the VPN, the panel can't know them, and the app keeps the last values it learned.

#Per-network memory

Colitu remembers what worked where, but this memory stays only on your device. A "network" means your connection type (Wi-Fi, mobile data, Ethernet) plus your internet provider's network. That is why your home Wi-Fi and your mobile data are remembered separately.

Old entries are deleted, and at most 200 entries are kept. A mode blocked on mobile data is still tried first on your home Wi-Fi.

#In what order are the modes tried?

• Android and iOS: Hysteria2 → VLESS Reality → VLESS XHTTP → Trojan → Shadowsocks 2022.
• Windows and Linux: Hysteria2 first. The TCP-based modes follow, sorted by the TCP connect time measured to the server, fastest first. Modes that can't be reached go last.
• Every app remembers the last mode that worked on each server for the network you are on for 24 hours and starts the next connection with it.

#Speed: how long does connecting take?

Usually a few seconds. The attempts are time-limited so you never hang:

• Each mode gets about 8 seconds (start-up plus traffic check).
• Each server gets about 20 seconds.
• A whole connection attempt takes at most about 45 seconds.

#Health check and reconnecting

A mode that merely looks connected isn't good enough. Colitu doesn't treat a connection as ready until it has confirmed that real traffic flows through the tunnel. The check asks common connectivity-test addresses (Cloudflare, Google, Microsoft) through the tunnel, not Colitu's own servers, and each mode gets about 4–6 seconds for it. If no traffic passes, the next mode is tried.

Before a mode is marked as not working, the app checks that your device is online at all. A dropped Wi-Fi isn't blamed on the mode.

Android shows Connected only after the check passes; until then it says Checking….

Monitoring continues after you're connected:

• Windows and Linux: the app checks the tunnel every few seconds and reconnects on its own if it stops carrying traffic.
• Android and iOS: if the connection drops unexpectedly, the app reconnects by itself (after about 2, 5 and 15 seconds, then shows the error). It also tries again when the network comes back.
• Nothing reconnects automatically if you pressed disconnect, signed out, or your plan or device is paused.

#Warm spare

While you are connected, the app can keep a second path ready inside the running connection. If the main path stops working, new traffic moves to the second path by itself and the VPN stays on. For how it works, what you will notice and how to turn it off, see Warm spare: why your connection doesn't drop.

#What happens when a protocol is blocked?

Some networks and some mobile operators block certain protocols. Colitu doesn't have to know which; it sees what doesn't work in the health check.

1. 1
   The blocked mode fails the health check and Colitu moves on to the next one. All you notice is that Connecting takes a little longer.
2. 2
   A mode that carried no traffic is tried last on that network for the next 6 hours. Your other networks are not affected: a mode blocked on mobile data is still tried first on your home Wi-Fi.
3. 3
   If none of a server's modes works, Colitu moves to the next server (see "server fallback" above).
4. 4
   The apps report to Colitu, in aggregate, which modes worked. This is used to improve the default order.

For example, if your network blocks UDP, Hysteria2 fails the check and Colitu switches to the TCP-based modes shortly after. You don't need to do anything.

#Server load

Servers report how many people are connected to them. This way a full server isn't offered to you, and users are spread across servers based on real numbers.

#Privacy

• Your country and your internet provider's network are worked out from your IP address on every request and are not stored.
• The per-network memory (which server and mode worked) stays only on your device.
• The health check goes to common connectivity-test addresses, not to Colitu's own servers.

For the full list of what is stored, see Privacy.

#What we don't publish

We name the protocols openly because they are open source technologies anyone can study. But server addresses, ports, SNI values and keys are never published anywhere; they are delivered to your app encrypted. This makes it much harder to block our servers in bulk.

#Protocol guides

• Hysteria2: speed over UDP and lossy networks
• VLESS Reality and XHTTP: camouflage for restricted networks
• Trojan and Shadowsocks 2022: fallback modes that look like HTTPS

Can't connect? See Connection problems or write to live support.

#Technical report

The current version is Adaptive Connect 3.0; its architecture, staged rollout, measurements and limits are in the Adaptive Connect 3.0 technical report. The design, measurement method and one-hour fault test of the previous version: Colitu Adaptive Connect 2.0 and Warm Spare: a technical report (previous version).