How a message reaches someone who isn't in range yet

A message, step by step

1. You send Priya a message. Your phone passes it to every Knit phone in range, and each of those passes it to the phones in range of them, up to eight hops out.
2. Priya is too far away, so it doesn't reach her yet. Sam was standing near you, though, and Sam's phone keeps a copy.
3. Sam wanders to the other side of the field. When Sam's phone comes into range of Priya's, it hands the message over.
4. Priya's phone opens it, and a delivery receipt starts back toward you the same way. When it reaches you, your message shows Delivered.

Sam doesn't have to do anything, and never sees your message. It's a direct message, which is end-to-end encrypted, so Sam's phone carries it sealed and has no way to open it. All Sam needed was Knit running in the background.

When a carried copy is handed on later, it sets off with a fresh eight hops. So a message can cross far more than eight phones, as long as people keep carrying it toward the other person.

What gets carried

Direct messages, group messages and posts in the Nearby room are all carried, along with the small things that go with them: reactions, delivery receipts, and changes to someone's name or status.

• Direct messages are offered to every phone your phone meets, so any of them can help get it to the person it's for.
• Group messages are offered only to members of that group. Your phone may carry a message for a group you aren't in, but when it hands one on later, it offers it only to phones on that group's member list.
• Nearby room posts are offered to everyone, because the room is open to everyone around. The room is plaintext by design: anyone in range can read it, including the phones carrying it.

How long a message is carried

Direct and group messages are carried for up to 24 hours after they're sent. Nearby room posts are carried for up to 6 hours, because the room is busier and is mostly about what's happening around you now.

When the time is up, every phone deletes its copy, delivered or not. The clock starts when the message is sent, not when each phone got it, so all the copies expire at about the same time.

How much one phone carries

Each phone carries up to 1,000 messages, counting reactions and receipts. No single person, group or the Nearby room can take more than 200 of those, so one busy conversation can't push everyone else's out. When a phone is full, it makes room by letting go of the oldest messages it's carrying for other people before any of your own.

What the ticks under your message mean

• Sent: the message is on its way. If nobody is in range yet, your own phone carries it and hands it on as soon as someone is.
• Delivered, in a direct message: the person you wrote to has it.
• Delivered, in a group: at least one member has it. The message's details show who else does, for example "Delivered to 3 of 5".
• Delivered, in the Nearby room: at least one person received it.
• Not sent yet — waiting for their key: you wrote to someone your phone can't seal a message for yet, often right after adding them from a link. It waits on your phone and goes out by itself once their key reaches you.

A receipt travels back the same way the message went, so Delivered can show up a while after the message actually arrived.