Guide to Blockstack Connect

Blockstack Connect is a Javascript library for integrating your application with Stacks v2. With Connect, you get some big benefits:


With yarn:

yarn add @blockstack/connect

With npm:

npm install --save @blockstack/connect



Every major method you’ll use with connect requires you to pass some options, like the name and icon of your app, and what to do when authentication is finished. In practice, this means you need to define these options, and pass them to the various API methods.

The exact interface you’ll use is defined as:

export interface AuthOptions {
  redirectTo: string;
  finished: (payload: FinishedData) => void;
  sendToSignIn?: boolean;
  userSession?: UserSession;
  appDetails: {
    name: string;
    icon: string;
parameter type default optional description
redirectTo string   false The path in your app where users go after sign in.
appDetails object   false an object which includes appName: string and appIcon: string. This will speed up the process of loading your app’s information during onboarding.
finished function   false A callback that can be invoked after authentication. This prevents having to do a whole page refresh in a new tab. One argument is passed to this callback, which is an object with userSession included. If included, then the redirectTo path is ignored, and the user will be logged in automatically.
sendToSignIn boolean false true Whether the user should go straight to the ‘sign in’ flow (false) or be presented with the ‘sign up’ flow (true) instead.
userSession UserSession   false pass a UserSession instance to use for authentication. If it’s not passed, @blockstack/connect will create one for you.

In React Apps

If you’re using connect in a React app, then the best option is to include connect’s React Provider and hooks in your React app.

First, setup the Connect provider at the “top-level” of your app - probably next to wherever you would put a Redux provider, for example.

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

const authOptions = {
  redirectTo: '/',
  finished: ({ userSession }) => {
  appDetails: {
    name: 'My Cool App',
    icon: '',

const App = () => (
  <Connect authOptions={authOptions}>
    // the rest of your app's components

Later, when you want to begin the onboarding process, use the useConnect hook to get connect’s doOpenAuth method.

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

const SignInButton = () => {
  const { doOpenAuth } = useConnect();

  return (
    <Button onClick={doOpenAuth}>
      Sign In

Sign In

To send the user straight to sign in, call doOpenAuth(true).

In ES6 (non-React) apps

If you aren’t using React, or just want a simpler API, then you can use the showBlockstackConnect method.

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

const authOptions = { /** See docs above for options */ };

Sign In

To send the user straight to sign in, include sendToSignIn: true in your authOptions.

Note about dependency size:

If you’re building a non-React app, note that importing @blockstack/connect will add React dependencies to your JavaScript bundle. We recommend using something like Webpack resolve aliases to replace react with preact in production, which reduces your bundle size. Check out our own webpack.config.js file to see how we use this for production builds.

If you’re using the hosted version of @blockstack/connect (described below), then you already have a production-optimized bundle.

Using a hosted version of @blockstack/connect

If you aren’t using ES6 imports, you can still use connect! We package the library so that it can be automatically used with unpkg.

First, include the script in your HTML:

<script src="" />

Then, you can use API methods under the blockstackConnect global variable:

const authOptions = { /** See docs above for options */ };

Handling redirect fallbacks

Connect is built to use popups with the window.postMessage API, which provides a much better and seamless user experience. However, there are times when this flow can fail. For example, the popup may be blocked, or the window.postMessage API might not work properly (which often happens on mobile browsers).

To make sure your app handles this gracefully, you’ll need to handle the case where authentication is performed through regular HTTP redirects. With redirects, your users will be sent back to your app at a URL like:


To finalize authentication with this flow, you’ll need to utilize the UserSession methods isSignInPending() and handlePendingSignIn(). For more information, check out the blockstack.js API reference.

const userSession = new UserSession(appConfig);

// ... call this code on page load
if (userSession.isSignInPending()) {
  const userData = await userSession.handlePendingSignIn();
  // your user is now logged in.