Understanding LNURL-Pay: How Lightning Addresses Really Work

LNURL-Pay is one of the most important UX improvements in the Lightning Network. It allows users to pay a Lightning Address (or LNURL) without manually requesting an invoice beforehand. Instead of sending money directly, LNURL-Pay defines a negotiation flow that tells wallets how to create and pay an invoice.

At its core, LNURL-Pay is about discovery and coordination, not payment execution.

smart247@walletofsatoshi.com

When a wallet sees this address, it derives the LNURL-Pay endpoint using a well-known path:

https://walletofsatoshi.com/.well-known/lnurlp/rustylip55

This URL is the LNURL-Pay endpoint. The wallet sends an HTTP request to this endpoint to understand how payments to this address should work.

Fetching Payment Rules

The LNURL-Pay endpoint responds with a JSON object describing the payment rules. A simplified example response looks like this:

{
  "minSendable": 1000,
  "maxSendable": 100000000,
  "callback": "https://domain.com/lnurl/callback/user",
  "metadata": "...",
  "tag": "payRequest"
}

This response answers key questions such as:

• How much can be paid?
  Defined by minSendable and maxSendable (in millisatoshis).

• Where do I request an invoice?
  Provided via the callback URL.

At this stage, no invoice exists yet. The wallet is simply learning the rules of engagement.

Requesting an Invoice

Once the wallet knows the acceptable payment range, the user selects an amount. The wallet then calls the callback URL, appending the chosen amount:

GET https://domain.com/lnurl/callback/user?amount=50000000

If the request is valid, the server responds with a BOLT11 Lightning invoice for that exact amount.

This is the critical step: LNURL-Pay doesn’t move funds—it only helps generate an invoice.

Paying the Invoice

After receiving the invoice, the wallet proceeds with a standard Lightning payment. From this point onward, everything follows the normal BOLT11 payment flow.

To summarize the wallet behavior:

1. Resolve Lightning Address → LNURL-Pay endpoint

2. Fetch payment rules

3. Request an invoice via callback

4. Pay the returned invoice

LNURL-Pay does NOT send money.

Instead, It negotiates payment terms and coordinates invoice creation, then relies on standard Lightning payments to move funds.

Think of LNURL-Pay as a protocol for asking how to pay, not for paying itself.

LNURL-Pay is a discovery and negotiation layer, not a payment rail.

Why LNURL-Pay Is Powerful

LNURL-Pay unlocks several key advantages for Lightning adoption:

• Reusable payment identifiers
  One address, unlimited payments.

• Human-readable addresses
  No more copy-pasting invoices.

• Wallet-to-wallet UX
  Payments feel instant and intuitive.

• Merchant-friendly flows
  Dynamic pricing, tips, and metadata support.

• Internet-native discovery
  Built on HTTPS and DNS—simple and robust.

Conclusion

LNURL-Pay = Fetch rules → request invoice → pay invoice