Questions

Do I need an account?

No. Each machine makes its own identity, a pair of keys, the first time it pairs. Nothing is registered anywhere.

Can the rendezvous read my files?

No. It introduces the two machines and, for offline contacts, holds sealed messages. File data goes directly between the machines and never through it. The threat model lists exactly what the rendezvous can see: who is online, when two machines meet, and how much sealed data passes.

What if someone overhears the code?

If they use it before your friend does, they get the file instead, and your friend's attempt fails. That is why codes are short-lived and work once. Read the code aloud or send it privately; for repeated transfers, pair, and codes go away.

Why are the codes so short?

Because the key exchange (CPace) only allows one guess per code. Three words give about two billion possibilities; a single guess almost never succeeds, and after it the code is dead. Long passwords protect against attackers who can try many times offline. Here nobody can.

How fast is it?

As fast as the slower of the two internet connections, in most cases. On a 40 ms path ferry moved 0.9 to 2.1 Gbit/s in testing (both ends on one busy machine); with 0.5% packet loss, 0.64 to 0.69, where a single TCP stream managed 0.4. See measurements.

Does it work behind a company or university network?

Often. ferry only sends directly, so a network that blocks UDP between the two machines stops it, and ferry says so. Then try another network, put one machine on a VPN or a tailnet, or, where you control the router, forward one UDP port: ferry config port 40000. ferry check shows what your network allows.

How big can a file be?

As big as the disk at the other end. Tested with 20 GiB files; nothing holds a whole file in memory, and each side uses a few hundred megabytes at most however large the transfer.

What happens if the transfer is interrupted?

Run the same send and get again, with a new code. The receiver keeps every piece that arrived and checked out, and asks only for the rest. A drop of a few seconds does not even interrupt the transfer.

Can I send to someone who is offline?

Messages, yes: they wait in a sealed mailbox for up to two weeks. Files need both machines online at the same time. ferry up keeps a machine reachable in the background; ferry up --unit prints a systemd unit for starting it at login.

Will ferry run something a contact sends me?

Never. ferry stores messages and files; it does not open or execute them. Fetched files lose their execute bit.

Where does ferry keep its data?

In ~/.config/ferry (or $FERRY_HOME): the identity, contacts, the message log, and files received while ferry up runs. The folder is readable only by you.

How do I remove a contact?

ferry forget sam. To talk again, pair again.

Why WebRTC?

It is the most widely deployed way to get two machines behind routers to talk directly, with encryption built in, and it runs in browsers too, which leaves the door open for a web version. Its usual weakness for bulk data, slow recovery from loss, is what ferry's multiple lanes address.