What is Keysend? To make a Lightning payment, the payee needs to generate a BOLT 11 invoice and then send it to the payer by email, displaying it as a QR code or other means. You can think of this invoice as a Bitcoin address in the Bitcoin network, even though it works substantially differently. The main difficulty is when the receiver can’t interact with the payer (e.g., because he doesn’t know who/when he’s getting paid, like anonymous donations, or when the receiver doesn’t have a channel to speak with the payer). Another is if the payee needs to accept reoccurring payments with varying amounts. This is where Lightning Keysend shines. Keysend removes the need for invoices when making payments. Instead, the receiver of the funds shares their node ID (a public key) once, and then the payer can pay any amount at any time in the future. Keysend doesn’t require changes to the network, but the receiving node needs to have Keysend support enabled.