Signing transactions

With Connect, you can interact with the Stacks 2.0 blockchain. You can allow your users to send transactions and interact with smart contracts.

How it works

For your app’s users to be able to execute a smart contract function, they need to sign and broadcast a transaction. It’s important that users remain control of the private keys that sign these transactions. Connect provides an easy-to-use workflow that allows your users to securely sign transactions.

Connect allows you to open the authenticator with parameters indicating the details of the transaction - like the smart contract address, function name, and specific arguments. Your users get the chance to see these details, and then sign and broadcast the transaction in a single click. Their transaction will be securely signed and broadcasted onto the Stacks blockchain. After this is done, a callback is fired to allow you to update your app.


Transaction signing is still in progress

The Stacks 2.0 blockchain is still in testnet, and our web app integration is also still in beta. In order to use transaction signing in your application, you need to use the configuration `authOrigin` with `@blockstack/connect`.

    const options = {
      // your other options
      authOrigin: ''


When signing a transaction, you need to specify a few details. Here is the exact interface that describes what options you have:

export interface ContractCallOptions {
  contractAddress: string;
  functionName: string;
  contractName: string;
  functionArgs?: any[];
  authOrigin?: string;
  userSession?: UserSession;
  appDetails?: AuthOptions['appDetails'];
  finished?: (data: FinishedTxData) => void;
parameter type default optional description
contractAddress string   false The Stacks address that published this contract
contractName string   false The name that was used when publishing this contract
functionName string   false The name of the function you’re calling. This needs to be a public function.
functionArgs array   false The arguments you’re calling the function with. You’ll need to provide the Clarity type with each argument. See the below section for details.
userSession UserSession   true A UserSession instance
appDetails object   false A dictionary that includes name and icon
finished function   false A callback that is fired when the transaction is signed and broadcasted. Your callback will receive an object back with a txId and a txRaw, both of which are strings.

Passing Clarity types with function arguments

To be able to serialize your transaction properly, you need to provide the appropriate Clarity type with each argument. These types are named the same as they are in Clarity. The value that you pass must be a string. The types you can pass are:

  • uint - i.e. "240"
  • int - i.e. "12"
  • bool - can be “true”, “false”, “0” or “1”
  • buff - i.e. "asdf"
  • principal - This can be a contract principal, or a standard principal. Examples: "ST22T6ZS7HVWEMZHHFK77H4GTNDTWNPQAX8WZAKHJ" or "".

Using these types, each argument is an object with the keys type and value. For example:

const functionArguments = [
    type: 'buff',
    value: 'hello, world'
    type: 'uint',
    value: '1'

If you’re using Typescript, these Clarity types can be imported as ContractCallArgumentType from @blockstack/connect.

Usage in ES6 (non-React) apps

import { openContractCall } from '@blockstack/connect';

// Here's an example of options:
const myStatus = 'hey there';
const options = {
  contractName: 'status',
  functionName: 'write-status!',
  functionArgs: [
      type: 'buff',
      value: myStatus,
  appDetails: {
    name: 'SuperApp',
    icon: ''
  finished: (data) => {
    console.log('TX ID:', data.txId);
    console.log('Raw TX:', data.txRaw);

await openContractCall(opts);

Usage in React Apps

Make sure you follow the setup instructions first. When you’re using useConnect, you don’t have to specify appDetails - we’ll pick that up from your existing configuration.

import { useConnect } from '@blockstack/connect';

const MyComponent = () => {
  const { doContractCall } = useConnect();

  const onClick = async () => {
    const opts = { /** See examples above */};
    await doContractCall(opts);

  return (
    <span onClick={onClick}>Call my contract</span>