LNURL

LNURL is a family of protocols that simplifies Lightning Network interactions by encoding an HTTPS endpoint that a wallet can call to negotiate payments automatically. Published as an open specification in 2019, it powers flows such as LNURL-pay, LNURL-withdraw, and LNURL-auth, and it underlies the human-readable lightning address format that looks like an email address.

Why it matters

Standard BOLT 11 invoices are single-use and amount-specific, which is awkward for tips, donations, and recurring payments. LNURL fixes this with static QR codes and identifiers that can be paid any amount, any number of times. A creator can print one code or publish one lightning address and receive payments indefinitely, with the wallet and server negotiating a fresh invoice behind the scenes each time.

LNURL-withdraw inverts the flow so services can push funds to users, and LNURL-auth lets a wallet log in to websites with a cryptographic signature instead of a password.

How it works

The wallet decodes the LNURL string into a web URL and sends a request. The server replies with JSON describing what is possible, such as minimum and maximum payment amounts. The wallet then requests a standard invoice for the chosen amount and pays it over Lightning as usual. Because the negotiation runs over HTTPS, LNURL requires the receiving service to run a web server, a tradeoff the fully peer-to-peer BOLT 12 offers standard aims to remove.