Guide to Blockstack Connect


Blockstack Connect is a JavaScript library for integrating Blockstack authentication and smart contracts into your app.

The library empowers you to:

  • Register new users with a pre-built onboarding flow that quickly educates them as to the privacy benefits of using your app with Blockstack and provisions a “Secret Key” that secures their identity and data against the Stacks blockchain.
  • Authenticate users when they return to your app using that same Secret Key.
  • Prompt users to sign transactions with smart contracts as written in Clarity and published to the Stacks blockchain.

How does this compare to blockstack.js?

Although blockstack.js can also be used to authenticate users, it implements the deprecated Blockstack Browser and lacks any pre-built onboarding UI that educates users as to how your app is more secure for having implemented Blockstack. As such, we advise that you use blockstack.js for all other functionality apart from authentication, such as saving and retrieving user data with Gaia.

Start building with Blockstack Connect

Head over to the Tutorial for App Integration to learn how to build apps with Blockstack Connect.


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 (true) or be presented with the ‘sign up’ flow (false) 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.

Design Guidance

Blockstack is valuable to users, but it can also be a barrier to those unfamiliar with Blockstack. The following guidelines serve to remedy that and help you onboard as many new users as you can.

Delay Blockstack onboarding as long as possible

People will often leave apps when things are asked of them before they experience the app. Give them a chance to try your app before you ask them to sign up with Blockstack. For example, a note taking app could let a new user write a couple of notes before prompting them to save their progress.

Provide an easy way in for new users

Many new users to your app will not be familiar with Blockstack yet and will be hesitant to click a Blockstack-branded button. Provide a generic button for users that are new to your app and Blockstack. Blockstack Connect will introduce new users to Blockstack and recognize existing users.

Design Guidance Example

Provide a quick way for existing users to sign in

You can point users to a specific part of the Blockstack App. For instance, a “Sign in” button on your website can redirect users to the sign in flow of the Blockstack App. If you do this, make sure you also have an option that is explicitly for new users and that points to the sign up flow.

To implement this functionality, check out our section on sending users to sign in immediately.