Keysend

💡 The Plain-English Definition

Keysend is a Lightning Network feature that lets you send a payment to any node without first requesting an invoice. Instead of the recipient generating a payment request, the sender pushes the payment directly — spontaneously, with no prior coordination.

🤔 But Why Though?

A standard Lightning payment needs an invoice from the recipient before anything moves. The recipient generates a payment hash and shares it in an invoice; the sender pays to that hash; the recipient reveals the secret to claim it. This handshake is secure and trustless, but it requires coordination — the recipient has to create an invoice before you can pay them. Often that’s fine. Sometimes it’s friction: tipping a creator, streaming tiny payments while you watch a video, or sending a spontaneous payment to a node whose address you know but haven’t spoken with. Those cases want the ability to pay first and sort out the rest later.

Keysend flips this: the sender generates the payment hash themselves, instead of getting it from the recipient. The sender picks a random secret, hashes it to make the payment hash, and tucks the secret (encrypted) inside the onion-routed payment — the layered-encryption method Lightning uses so no middle node sees the whole route. When the payment reaches the destination node, it finds the encrypted secret, decrypts it, and uses it to claim the funds. The recipient never had to prepare anything.

There’s a privacy tradeoff worth understanding. Because the sender made the hash rather than receiving it from the recipient, there’s no cryptographic proof that the recipient got the payment and chose to reveal the secret — the sender revealed it on their own. So for cases where proof of payment matters, ordinary invoice-based payments are the better fit. For spontaneous, low-stakes payments, keysend’s convenience is worth the limitation.

🌍 The Real-World Analogy

A standard Lightning payment with an invoice is like wiring money to a specific reference number the recipient gives you — they hand you the reference, you send to it, they confirm receipt. Keysend is like slipping cash under someone’s door without knocking — you know where they live (their node’s public key), you decide the amount, and you push it through. They receive it without ever generating a request. The tradeoff: you can’t prove they “signed for” it, but for casual or streaming payments, that’s fine.