Web client
The cryptography runs as WebAssembly compiled from the same core the native builds use. This page never holds a key — only the text you are reading.
An ID has been generated for you. Give it to the other person directly — there is no registration and no directory, which is also why nobody can find you without being told.
The passphrase encrypts this device's identity and history. It cannot be reset — there is no server-side recovery, deliberately, because a recovery path the server can trigger is one it can be compelled to trigger.
Web client
This device has a saved identity. Your passphrase decrypts it — nothing was sent anywhere.