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Substrate Connect

Substrate connect provides a way to interact with substrate based blockchains in the browser without using an RPC server. Substrate connect uses a smoldot WASM light client to securely connect to the blockchain network without relying on specific 3rd parties.

Due to browser limitations on websockets from https pages, establishing a good number of peers is difficult as many nodes need to be available with TLS. Substrate connect provides a browser extension to overcome this limitation and to keep the chains synced in the background, which makes your apps faster.

When building an app with substrate connect, it will detect whether the user has the extension and use it, or create the WASM light client in-page for them.

Substrate connect builds on Polkadot JS so building an app is the same experience as with using a traditional RPC server node.

The substrate connect API documentation is published here.


This repository is using pnpm workspaces.

We also use corepack, which ensures that the correct version of pnpm is used.

Please see our contributing guidelines for details on how we like to work and how to smoothly contribute to the project.

Getting Started

If you're hacking on this repository, here's how to install everything and spin up a demo:

  1. Install any prerequisites. These steps were tested with:
    • Node.js (node) v20.9.0.
    • pnpm 9.0.6 (npm install -g pnpm).
    • corepack 0.20.0 (This should be bundled with recent Node.js versions).
  2. Clone the repository.
    • git clone
    • cd substrate-connect to navigate to the repository root.
  3. Install the dependencies.
    • corepack pnpm install
  4. In terminal A, run cd projects/extension && corepack pnpm dev.
  5. In terminal B, run cd projects/extension && corepack pnpm start.
    • This will open a Chrome browser window with the extension pre-loaded.
    • Make sure that the extension is running.
  6. In terminal C, run cd projects/demo && corepack pnpm dev.
    • Navigate to the URL that this logs in the Chrome browser that opened in 5.
    • You should see the extension come to life and the demo app log latest blocks.

To clean up all build artefacts in workspaces in the repository, run:

corepack pnpm clean

To clean up all build artefacts and dependencies in workspaces in the repository, run:

corepack pnpm deep-clean


Visit the release doc and follow the steps there to release a new version of the extension.

Useful Links

Substrate Connect Documentation Page

Download at:


Run Wasm Light Clients of any Substrate based chain directly in your browser.



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