Kind 9735: Zap

Overview

Zap events (kind 9735) represent lightning network payments between Nostr users. They are created by lightning nodes or services when a zap invoice generated from a zap request has been paid. Zaps allow users to send Bitcoin tips to each other and have them recorded in the Nostr ecosystem, creating a visible history of payments that can be displayed by clients.

Specification

Property	Value
Kind Number	9735
Event Range	Regular
Defined in	NIP-57

Content Format

The content field of a zap receipt is typically empty.

Schema

""

Tags

Tag Name	Description	Format	Required
p	Recipient's public key	["p", "<pubkey-hex>"]	Yes
P	Sender's public key (from zap request)	["P", "<pubkey-hex>"]	No
e	Event being zapped (if any)	["e", "<event-id>"]	No
a	Addressable event coordinate (if any)	["a", "<kind>:<pubkey>:<d-tag>"]	No
bolt11	Lightning invoice	["bolt11", "<invoice>"]	Yes
description	JSON-encoded zap request	["description", "<encoded-json>"]	Yes
preimage	Payment preimage	["preimage", "<preimage-hex>"]	No
amount	Amount in millisatoshis	["amount", "21000"]	Recommended

Client Behavior

Clients should:

1. Validate zap receipts as described in NIP-57, including checking that the pubkey matches the expected nostrPubkey from the recipient's LNURL provider.
2. Display zaps on profiles and posts where they occurred, typically showing the amount paid and by whom.
3. Parse the zap request from the description tag if additional metadata is needed.
4. When receiving a valid zap receipt, consider it proof that a payment has been made.
5. Support both direct zaps to users and zaps to specific events.
6. Handle multi-recipient zaps according to the weight values when zapping events with zap tags.

Relay Behavior

Relays should:

1. Handle zap receipts like any other event.
2. Store them according to normal event policies.
3. Make them available to clients requesting them with appropriate filters.

Use Cases

• Tipping content creators for valuable posts
• Paying for access to resources or content
• Rewarding users for helpful information
• Supporting favorite profiles with recurring payments
• Revenue stream for creators
• Spam prevention by requiring zaps for certain actions

Example

{
  "id": "67b48a14fb66c60c8f9070bdeb37afdfcc3d08ad01989460448e4081eddda446",
  "pubkey": "9630f464cca6a5147aa8a35f0bcdd3ce485324e732fd39e09233b1d848238f31",
  "created_at": 1674164545,
  "kind": 9735,
  "tags": [
    ["p", "32e1827635450ebb3c5a7d12c1f8e7b2b514439ac10a67eef3d9fd9c5c68e245"],
    ["P", "97c70a44366a6535c145b333f973ea86dfdc2d7a99da618c40c64705ad98e322"],
    ["e", "3624762a1274dd9636e0c552b53086d70bc88c165bc4dc0f9e836a1eaf86c3b8"],
    ["bolt11", "lnbc10u1p3unwfusp5t9r3yymhpfqculx78u027lxspgx..."],
    ["description", "{\"pubkey\":\"97c70a44366a6535c145b333f973ea86dfdc2d7a99da618c40c64705ad98e322\",\"content\":\"\",\"id\":\"d9cc14d50fcb8c27539aacf776882942c1a11ea4472f8cdec1dea82fab66279d\",\"created_at\":1674164539,\"sig\":\"77127f636577e9029276be060332ea565deaf89ff215a494ccff16ae3f757065e2bc59b2e8c113dd407917a010b3abd36c8d7ad84c0e3ab7dab3a0b0caa9835d\",\"kind\":9734,\"tags\":[[\"e\",\"3624762a1274dd9636e0c552b53086d70bc88c165bc4dc0f9e836a1eaf86c3b8\"],[\"p\",\"32e1827635450ebb3c5a7d12c1f8e7b2b514439ac10a67eef3d9fd9c5c68e245\"],[\"relays\",\"wss://relay.damus.io\",\"wss://nostr-relay.wlvs.space\",\"wss://nostr.fmt.wiz.biz\",\"wss://relay.nostr.bg\",\"wss://nostr.oxtr.dev\",\"wss://nostr.v0l.io\",\"wss://brb.io\",\"wss://nostr.bitcoiner.social\",\"ws://monad.jb55.com:8080\",\"wss://relay.snort.social\"]]}"],
    ["preimage", "5d006d2cf1e73c7148e7519a4c68adc81642ce0e25a432b2434c99f97344c15f"],
    ["amount", "1000000"]
  ],
  "content": "",
  "sig": "908a15e46fb4d8675bab026fc230a0e3542bfade63da02d542fb78b2a8513fcd0092619a2c8c1221e581946e0191f2af505dfdf8657a414dbca329186f009262"
}

References

• NIP-57: Lightning Zaps
• Lightning Network specification
• LNURL specification

Related Kinds

• Kind 9734: Zap Request - Request for a zap invoice
• Kind 9041: Zap Goal - Fundraising campaign with zaps

Notes

• Zap receipts are not considered absolute proof of payment as they could be forged, but they are trusted within the context of the ecosystem.
• The pubkey of a zap receipt is the public key of the recipient's LNURL provider, not the recipient or sender.
• The created_at timestamp should match the time when the invoice was paid.
• The zap flow involves multiple entities: the sender (requester), the recipient's LNURL server, and the lightning network.
• Future improvements may include encrypted zap requests for more privacy.