Five concrete situations.

Lattice isn't useful for everyone. It's useful for these five situations. If you don't recognise yourself in any of them you probably don't need it. If you do, install it now while everything's calm.

1. You and your family during a regional internet shutdown.

Iran, Myanmar, Sudan, Belarus. Some governments switch the internet off, sometimes for an afternoon and sometimes for weeks. WhatsApp, Signal and iMessage all go quiet. Lattice doesn't, because it doesn't use the internet to deliver messages in the first place.

What it can do is keep you in touch with family in your city, hopping through other Lattice users between you. That's enough to confirm everyone's okay, agree on a meeting place, or pass on a piece of news.

What it can't do is reach a relative in another city, unless someone carries the message between cities, or there's long-range radio in the chain (LoRa or a Meshtastic device), or the internet comes back. Why physics says so.

2. You and friends at a festival or event.

Glastonbury, a stadium gig, a packed New Year's Eve. Every cell tower in the area is at capacity. Texts don't go through, group calls drop, and WhatsApp loads two-day-old messages because the data link is choking.

Lattice likes a dense crowd. The more nearby phones running it, the better the routing works. There's a coarse "where's my friend?" feature on the same mesh, where each phone tells its verified contacts its rough location every few minutes. And you can suggest a meeting point: Lattice works out the centroid of the group and drops a pin everyone can see.

3. You and your kids during a disaster.

Earthquake, hurricane, wildfire, flood. The towers are down and the power's out. You don't know if the kids made it home from school. Lattice on their phone, Lattice on yours, a few minutes of battery each, and you've got a working messenger.

The check-in feature was built for exactly this. Once a month it nudges you to send a "still here?" to your handful of most important people, so you know the lines work before the day you need them.

4. You and someone in a country where messengers are blocked.

Journalists, the family of dissidents, activists, researchers fielding sources in restrictive regimes. The usual Western messengers are sometimes blocked outright, sometimes monitored, and sometimes still working but visibly so, where the visibility itself is the danger.

Be clear about what Lattice helps with here and what it doesn't. It encrypts the contents of your messages with end-to-end and post-quantum cryptography, so an observer reads nothing. It does not hide the fact that you're running Lattice, since the radios are detectable to anyone in range. For high-threat use, read the threat model in WP-01 and the limits in WP-05.

5. You as a parent or partner who just wants to be ready.

You don't think you need it and you don't expect a disaster. But you'd rather have it installed than not, the same way you keep a torch in a drawer.

This is the case for installing it just in case. Lattice is built to cost you almost nothing while it waits. After a week without use it slips into a low-power "Standby" mode, and after a month it goes "Dormant" and barely scans at all. It shouldn't drain your battery while you don't need it. How dormancy works.

Once a month it nudges you to send a one-tap test message to your important people, so the lines stay warm. That's the whole maintenance burden.

What if you're not in any of these situations?

Then Lattice is probably not for you. It isn't a daily-driver messenger, and WhatsApp and Signal are excellent at that job. Lattice is the standby tool, a piece of safety equipment for the day normal communication doesn't work.

If you only ever use it once, the day you use it, it'll have earned its place on your phone.