CruiseLink
Messaging apps that work without internet
They exist, and they all work the same way: the phones talk straight to each other over Bluetooth or a local network instead of going through the internet. The catch is always the same too — everyone has to have installed it beforehand, because nothing installs with no connection.
This page is the honest survey, including the parts that disappoint people. We build one of these, so take the section about our own with appropriate scepticism and check it against the measurements.
The four things that actually exist
1. Bluetooth and local-network apps
Your phone finds other phones nearby and hands the message across directly. Many also pass messages along through other people's phones, so a note can travel further than one radio reaches — carried by somebody walking, rather than transmitted.
What it genuinely does: messages, free, with no account and no signal, between people who are in roughly the same place. Where it fails: everybody needs it installed first, and if only two or three people in a large building or on a large ship have it, there is no network to speak of. That is the single commonest reason these apps disappoint, and it is nothing to do with the radio.
2. SMS
Worth saying because people forget it: a plain text message needs a mobile signal, not internet. Somewhere with wifi down but a phone mast working, SMS still goes. Somewhere with no mast — at sea, up a mountain, on a plane — it does not.
3. Satellite messaging
Recent iPhones and some Android phones can send messages over satellite, and dedicated satellite messengers have done it for years. It is the only thing on this list that reaches someone far away with no network at all.
It wants a clear view of the open sky, it is slow by comparison with everything else, and the free tiers are built around emergencies rather than chat.
Stated from the manufacturers' own documentation rather than from our own testing. We have not tried satellite messaging at sea and do not claim it works there.
4. Local wifi with no internet
Two devices on the same wifi network can often reach each other even when that network has no working internet, or when the internet behind it is behind a paywall. This is the quiet one nobody expects, and on some cruise ships it is exactly what happens: the captive portal charges for the internet, not for the ship's own network. It is a bonus where it exists rather than something to rely on.
The honest limits, which every one of these shares
- Install first. Every single person has to have the app before the connection goes. There is no way around this, and it is where most attempts fall down.
- Near, or carried. A message reaches someone when their phone is close enough, or when somebody else with the app moves between you. Nothing else.
- Not instant. Expect minutes rather than seconds when people are spread out, and be suspicious of any app that implies otherwise.
- Your people, not strangers. An app that needs hundreds of strangers nearby to work is an app that works in a demonstration and not on your holiday.
What the numbers look like when it does work
From our own logs, and measured rather than estimated. A family of six spent four hours together with no shared wifi — a meal, then an arcade, moving around in pairs. One Android phone's record of that evening:
| Completed exchanges per hour | Same person re-found every | |
|---|---|---|
| Sitting still at dinner | 90 | 4.2 and 4.4 minutes |
| Walking round an arcade | 60 | 6.0 and 7.4 minutes |
317 completed exchanges, every one over Bluetooth and none over wifi. Moving about cost about a third of the throughput and roughly two minutes of gap. It did not stop it — a phone that moves is a phone that carries messages.
Across a longer run on two Android handsets, a person the phone had already met was re-reached on 99.8% and 99.6% of attempts, over 3,007 and 874 tries. The full set of measurements, including the attempt that failed, is here.
Ours, and what it is not
CruiseLink is one of these apps, built for one situation: a group of people on a cruise ship who do not all want to buy the ship's internet. It is free, there is no account, and it works between iPhones and Android phones in the same group.
It is deliberately narrow. It does not try to be a mesh across a whole ship full of strangers, because that needs a density of users no new app has. It carries messages between the people you came with. If that is your problem, it is a good fit; if you want to reach somebody a hundred miles away with no signal, it is the wrong tool and so is everything else on this list except satellite.
Get CruiseLink
Free, no account, nothing to set up beyond your group. On iPhone and Android, and the two work together.
