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The BNS client is a library for Javascript developers who want to build BNS apps.

This library has a few main components:

  • BNSApiClient - an interface to the BNS API
  • BNSContractsClient - an interface to all BNS and BNSx contracts
  • A set of types and utility functions for working with BNS

Interacting with the BNS API

The default base URL for all API queries is

Create the API client

import { BnsApiClient } from "@bns-x/client";

const bns = new BnsApiClient();

// optionally, set base URL:
// new BnsApiClient('');

Get the "display name" for an address

Returns: string | null

The logic for returning a user's "display name" is:

  1. If the user owns any BNS Core names, return that name
  2. If the user has a subdomain, return that
  3. If the user owns a BNSx name, return that name
const address = "SP123...";
const name = await bns.getDisplayName(address);

Get details about a name

You can call getNameDetails two different ways:

  • getNameDetails(name) - where name is a fully-qualified name (like example.btc)
  • getNameDetails(name, namespace)

Returns: NameInfoResponse | null

const details = await bns.getNameDetails("example.btc");
// equivalent to:
// const details = await bns.getNameDetails('example', 'btc');

If the name doesn't exist, the function returns null.


  • address: the owner of this name
  • expire_block: the block height this name expires at
  • zonefile: zonefile for the name
  • isBnsx: a boolean indicating whether the name has migrated to BNSx

If the owner of the name has inscribed their zonefile, it also returns:

  • inscriptionId: the ID of the inscription containing the zonefile
  • inscription: object containing:
    • blockHeight: Bitcoin block height where the name was inscribed
    • timestamp: timestamp of the inscription's creation date
    • txid: Bitcoin txid where the inscription was created
    • sat: the "Sat" holding the inscription

If the name has been migrated to BNSx, this response also includes:

  • id: the NFT ID (integer)
  • wrapper: the wrapper contract that owns this name

Fetch multiple names owned by an address

Returns: NamesByAddressResponse

If you want to fetch multiple names (both BNS and BNSx) owned by an address, you can use this function. Note that if you just want to show a name for an address, using getDisplayName will have better performance.

const allNames = await bns.getAddressNames(address);

The return type has these properties:

  • names array of names (strings) the user owns
  • displayName a single name to show for the user (see getDisplayName)
  • coreName the address's BNS Core name, if they have one
  • primaryProperties: The properties of the address's primary BNSx name (see nameProperties)
  • nameProperties: properties for the address's BNSx names
    • id: numerical ID of the name
    • combined: the full name (ie example.btc)
    • decoded: if the name is punycode, this will return the UTF-8 version of the name
    • name and namespace: the separate parts of the name (ie example and btc for example.btc)

Interacting with BNS and BNSx contracts

This package includes clarigen generated types and functions for interacting with BNS contracts.

The BnsContractsClient

Create a new client by specifying the network you're using. It can be one of mainnet, testnet, or devnet. This is used to automatically set the correct contract identifier for your network.

For calling read-only functions, you can also specify a Stacks API endpoint as the second parameter.

import { BnsContractsClient } from "@bns-x/client";
// defaults to "mainnet"
export const contracts = new BnsContractsClient();

// For other networks:
// new BnsContractsClient('testnet', '');

Interacting with specific contracts

The contracts client includes getters for various BNSx and BNS contracts:

  • registry: the main name registry contract for BNSx
  • queryHelper: a contract that exposes various query-related helpers
  • bnsCore: the BNS Core contract
  • upgrader: the contract responsible for upgrading wrapped names to BNSx

Usage with Clarigen

Refer to the clarigen docs for more information - but here are a few quick examples.

In each example, contracts refers to an instance of the BnsContractsClient.

Generate a ClarigenClient

import { ClarigenClient } from "@clarigen/web";
// Uses micro-stacks for network information
import { microStacksClient } from "./micro-stacks";

export const clarigen = new Clarigen(microStacksClient);

Call read-only functions

Learn more

const primaryName = await

// `roOk` is a helper to automatically expect and scope to a function's `ok` type
const price = await clarigen.roOk(
contracts.bnsCore.getNamePrice(nameBuff, namespaceBuff)

Make transactions

Learn more

import { useOpenContractCall } from "@micro-stacks/react";

const registry = contracts.registry;

export const TransferName = () => {
const { openContractCall } = useOpenContractCall();
const nameId = 1n;

const makeTransfer = async () => {
await openContractCall({
id: nameId,
sender: "SP123...",
recipient: "SP123...",
// ... include other tx args
async onFinish(data) {
console.log("Broadcasted tx");

return <button onClick={() => makeTransfer()}>Transfer</button>;

Examples of interacting with contracts:

BNS Core

Generate a pre-order tx:

import { asciiToBytes, randomSalt, hashFqn } from "@bns-x/client";

const name = "example";
const namespace = "btc";
const price = 2000000n;

const salt = randomSalt();
const hashedFqn = hashFqn(name, namespace, salt);

const tx = contracts.bnsCore.namePreorder({
hashedSaltedFqn: hashedFqn,
stxToBurn: price,

Later, register the name:

const register = contracts.bnsCore.nameRegister({
name: asciiToBytes(name),
namespace: asciiToBytes(namespace),
zonefileHash: new Uint8Array(),

Transfer a BNSx name

id: 1,
sender: "SP123..",
recipient: "SP123..",

Unwrap a BNSx name

Because each wrapper contract is at a different address, the client exposes a helper function for creating a "wrapper instance" at a specific address.

const contractId = "";
const wrapperContract = contracts.nameWrapper(contractId);

// now can interact with its functions
// wrapperContract.unwrap(...)

This example uses both the API and contracts client.

const nameDetails = await bnsApi.getNameDetailsFromFqn("example.btc");

if (!nameDetails.isBnsx) throw new Error("Cant unwrap name");

const { wrapper } = nameDetails;

const wrapperContract = contracts.nameWrapper(wrapper);

// you can specify a different recipient for the unwrapped name.
// If not specified, it defaults to the owner of the BNSx name.

wrapperContract.unwrap(); // sends BNS name to current BNSx owner

// send to different address:
recipient: "SP123...asdf",

Getting source code for a name wrapper contract

If you need to deploy a name wrapper contract, you can get the source code from nameWrapperCode.

const code = contracts.nameWrapperCode();


This library exposes a few functions to make it easier to get records from a name's zonefile.

The ZoneFile class can be constructed with a zonefile (string) and can be used to easily get information from the zonefile.

Getting a BTC address

import { ZoneFile, BnsApiClient } from "@bns-x/client";

const client = new BnsApiClient();

// Returns `string | null`;
export async function getBtcAddress(name: string) {
const nameDetails = await client.getNameDetailsFromFqn(name);
if (nameDetails === null) {
// name not found
return null;
const zonefile = new ZoneFile(nameDetails.zonefile);

// Returns `null` if `_btc._addr` not found in zonefile
return zonefile.btcAddr;

Get an arbitrary TXT record

If you want to get the TXT record for any specific key, you can use getTxtRecord.

const zonefile = new ZoneFile(nameDetails.zonefile);
const txtValue = zonefile.getTxtRecord("_eth._addr"); // returns `string | null`

Utility functions

This library exposes a few utility functions that come in handy when working with BNS.

asciiToBytes and bytesToAscii

In BNS, all names are stored on-chain as ascii-converted bytes.

import { asciiToBytes, bytesToAscii } from "@bns-x/client";

// the human-readable version of the name:
const name = "example";

// the name stored on chain
const nameBytes = asciiToBytes(name);

// convert from on-chain:
bytesToAscii(nameBytes) === name;


When preordering a name on BNS, you need to create a random salt.

import { randomSalt } from "@bns-x/client";
const salt = randomSalt(); // Uint8Array


When preordering a name, you need to create a "hashed salted fully qualified name". This helper function generates that for you.

import { asciiToBytes, randomSalt, hashFqn } from "@bns-x/client";

const name = "example";
const namespace = "btc";

const salt = randomSalt();
const hashedFqn = hashFqn(name, namespace, salt);


If you have a string, you can parse it into individual parts:

import { parseFqn } from "@bns-x/client";
const name = parseFqn("example.btc");; // 'example'
name.namespace; // 'btc'
name.subdomain; // undefined

// { name: 'example', namespace: 'btc', subdomain: 'sub' }


Helper function to expose namespaces that do not expire.

Note: This is a hard-coded list. If new namespaces are registered, they are not automatically added to this list.

If you want to fetch on-chain data, use BnsContractsClient#fetchNamespaceExpiration.

Also exposed is NO_EXPIRATION_NAMESPACES, which is a set of strings.

import { doesNamespaceExpire, NO_EXPIRATION_NAMESPACES } from "@bns-x/client";

doesNamespaceExpire("stx"); // returns false
NO_EXPIRATION_NAMESPACE.has("stx"); // returns true


This package includes a few punycode-related functions and utilities. Note: if you only want the punycode functions, you can import them from @bns-x/punycode.

Under the hood, the @adraffy/punycode library is used.


Converts a punycode string to unicode.

import { toUnicode } from "@bns-x/client";

toUnicode("xn--1ug66vku9r8p9h.btc"); // returns '🧔‍♂️.btc'


Convert a unicode string to punycode.

import { toPunycode } from "@bns-x/client";

toPunycode("🧔‍♂️.btc"); // returns 'xn--1ug66vku9r8p9h.btc'

Zero-width-join characters and modifiers

In Emoji, there are various "zero-width" or invisible characters that are part of a valid "emoji sequence". However, some users add invalid ZWJ characters to a name in order to try and trick other users into thinking that a name just a single emoji.

This library exposes some functions for determining whether a string contains extra invalid ZWJ characters. It will not flag valid ZWJ sequence emojis.

import { hasInvalidExtraZwj } from "@bns-x/client";

const badString = "🧜🏻‍"; // {1F9DC}{1F3FB}{200D} - extra `200D` at end

hasInvalidExtraZwj(badString); // true

const goodString = "🧔‍♂️"; // {1F9D4}{200D}{2642}{FE0F}

hasInvalidExtraZwj(goodString); // false, even though there are ZWJ characters


For apps like marketplaces that want to show both a punycode and unicode name, as well as flag if there is an invalid ZWJ modifier, fullDisplayName creates a string that is appropriate for regular, punycode, and invalid punycode names.

import { fullDisplayName } from "@bns-x/client";

// regular names:
fullDisplayName("example.btc"); // "example.btc"

// punycode names:
fullDisplayName("xn--1ug66vku9r8p9h.btc"); // 'xn--1ug66vku9r8p9h.btc (🧔‍♂️.btc)'

// punycode with extra ZWJ
fullDisplayName("xn--1ug2145p8xd.btc"); // 'xn--1ug2145p8xd.btc (🧜🏻‍.btc🟥)'