JavaScript library to interact with interBTC and kBTC

Usage no npm install needed!

<script type="module">
  import interlayInterbtcApi from 'https://cdn.skypack.dev/@interlay/interbtc-api';




The interBTC TypeScript library connects the Polkadot and Kusama ecosystems with Bitcoin. It allows the creation of interBTC on Polkadot and kBTC on Kusama, fungible "wrapped" tokens that represent Bitcoin. Wrapped tokens are backed by Bitcoin 1:1 and allow redeeming of the equivalent amount of Bitcoins by relying on a collateralized third-party (Vaults). In comparison to other bridge constructions (like tBTC, wBTC, or RenVM) anyone can become an intermediary by depositing collateral making interBTC the only truly open system.

The bridge itself follows the detailed specification: Explore the specification »

It is implemented as a collection of open-source Substrate modules using Rust: Explore the implementation »

Built with

You can visit bridge.interlay.io to see the library in action.


The library assumes you have a version of the Interlay or Kintsugi networks running locally or remotely.

Creating an API Instance

To use the library, you will first need to create a PolkadotJS APIPromise instance, and then instantiate a InterBtcApi instance.

import { createInterBtcApi } from "@interlay/interbtc";

// If you are using a local development environment
// const PARACHAIN_ENDPOINT = "ws://";
// if you want to use the Interlay-hosted beta network
const PARACHAIN_ENDPOINT = "wss://api.interlay.io/parachain";
const isMainnet = false;
const interBTC = await createInterBtcApi(PARACHAIN_ENDPOINT, isMainnet);

Attaching an Account

To emit transactions, an account has to be set. The account should conform to the AddressOrPair interface. If the account is not of the KeyringPair type, then a signer must also be provided (such as an injected extension signer, from the Polkadot wallet). See more details here: https://polkadot.js.org/docs/extension/usage/

import { createTestKeyring } from "@polkadot/keyring/testing";
const keyring = createTestKeyring();
const keypair = keyring.getPairs()[0];

The different functionalities are then exposed through the InterBtcApi instance.

Issuing interBTC

From the account you set, you can then start requesting to issue interBTC.

import { BitcoinAmount } from "@interlay/monetary-js";
// amount of BTC to convert to interBTC
// NOTE: the bridge fees will be deducted from this. For example, if you request 1 BTC, you will receive about 0.995 interBTC
const amount = BitcoinAmount.from.BTC(0.001);
// request to issue interBTC
const requestResults = await interBTC.issue.request(amount);
// the request results includes the BTC address(es) and the BTC that should be sent to the Vault(s)
// NOTE: the library will automatically distribute issue requests across multiple Vaults if no single Vault can fulfill the request.
// Most of the time, a single Vault will be able to fulfill the request.

At this point, you will need to send BTC using your favorite BTC wallet.

Redeeming interBTC

import { BitcoinAmount } from "@interlay/monetary-js";
// the amount wrapped tokens to redeem
// NOTE: the bridge fees will be deducted from this 
const amount = BitcoinAmount.from.BTC(0.001);
// your BTC address
const btcAddress = "tb123....";
// the request results includes the BTC address(es) and the BTC that should be sent to the Vault(s)
// NOTE: the library will automatically distribute redeem requests across multiple Vaults if no single Vault can fulfill the request.
// Most of the time, a single Vault will be able to fulfill the request.
const requestResults = await interBTC.redeem.request(amount, btcAddress);

At this point, one more more Vaults will send BTC to the address specified within 24 hours.

More Examples

There are plenty more examples how to use this library. Best is to take a look at the integration tests: https://github.com/interlay/interbtc-api/tree/master/test/integration

API Documentation

Please check the documentation at https://docs.interlay.io/interbtc-api/#/classes/DefaultInterBtcApi


Clone this Repository

cd interbtc-api

Setting up a Local Development Environment

You can spin up the parachain including the different clients with docker-compose:

docker-compose up

If you want to run components individually, you can clone the repositories and run the commands as done in docker-compose.yml.

To install dependencies, run

yarn install

Build the library using

yarn build


To run only unit tests, use

yarn test:unit

Note that the parachain needs to be running for all tests to pass.

Then, to run tests, run

yarn test

Certain API calls require a parameter of type AccountId, which represents the Polkadot/Kusama account and can be instantiated as follows

import { AccountId } from "@polkadot/types/interfaces/runtime";

const activeStakedRelayerId = await interBTC.api.createType(
const feesEarnedByActiveStakedRelayer = await interBTC.stakedRelayer.getFeesEarned(

Updating Types

Run the parachain (or indeed any Substrate node) and download the metadata:

curl -H "Content-Type: application/json" -d '{"id":"1", "jsonrpc":"2.0", "method": "state_getMetadata", "params":[]}' http://localhost:9933 > src/json/parachain.json

Then, update the metadata by building the library:

yarn build

Usage as script

This library can be used as a script for initializing a local interBTC setup (the services ran using docker-compose), to allow for manual testing of the UI.

yarn install
yarn initialize

By default, every flag is enabled. To get more information about the flags and disable some of them, run

yarn initialize --help


Bitcoin Regtest

Regtest is a local Bitcoin instance that allows you to practically anything including sending transactions, mining blocks, and generating new addresses. For a full overview, head over to the Bitcoin developer documentation.

Sending Transactions

For the issue process, you need to send a transaction. On regtest this can be achieved with:

bitcoin-cli -regtest -rpcwallet=Alice sendtoaddress VAULT_ADDRESS AMOUNT

Mining Blocks

In regtest, blocks are not automatically produced. After you sent a transaction, you need to mine e.g., 1 block:

bitcoin-cli -regtest generatetoaddress 1 $(bitcoin-cli -regtest getnewaddress)

Getting Balances

You can query the balance of your wallet like so:

bitcoin-cli -regtest -rpcwallet=Alice getbalance


You can hard-reset the docker dependency setup with the following commands:

docker kill $(docker ps -q)
docker rm $(docker ps -a -q)
docker rmi $(docker images -q)
docker volume rm $(docker volume ls -q)


Contributions are what make the open source community such an amazing place to be learn, inspire, and create. Any contributions you make are greatly appreciated.

  1. Fork the Project
  2. Create your Feature Branch (git checkout -b yourname/AmazingFeature)
  3. Commit your Changes (git commit -m 'Add some AmazingFeature')
  4. Push to the Branch (git push origin yourname/AmazingFeature)
  5. Open a Pull Request

If you are searching for a place to start or would like to discuss features, reach out to us:


(C) Copyright 2022 Interlay Ltd

interbtc-js is licensed under the terms of the Apache License (Version 2.0). See LICENSE.


Website: Interlay.io

Twitter: @interlayHQ

Email: contact@interlay.io


We would like to thank the following teams for their continuous support: