Definition
A Lightning invoice in the BOLT11 format is a single bech32-encoded string that encodes everything a sender needs to make a Lightning payment. It is the standard payment-request format on the network, the long lnbc... string you scan or paste to pay someone.
What's inside the string
A BOLT11 invoice carries a payment hash (the SHA-256 of a secret preimage the recipient holds), an optional amount, a human-readable description or its hash, an expiry (commonly one hour), and the recipient's public key. It may also include route hints that help senders reach a recipient whose channels are private, listing details like the peer's pubkey, short channel ID, fee base, fee rate, and CLTV delta. The whole payload is signed by the recipient's node.
How it drives a payment
The sender never sees the preimage, only its hash, which is what keeps the downstream routing trust-minimized. The sender's node uses the encoded data to find a route and construct a chain of HTLCs all locked to that payment hash. When the recipient reveals the preimage to claim payment, it proves receipt and cascades the settlement back along the path.
BOLT11 is one of the most widely used parts of the BOLT specification. A newer format, BOLT12 "offers," adds reusability and improved privacy, but BOLT11 remains the dominant invoice standard across routing nodes today.
In Simple Terms
A Lightning invoice in the BOLT11 format is a single bech32-encoded string that encodes everything a sender needs to make a Lightning payment. It is…