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Polkadot API

Polkadot API is a TypeScript library suite for building applications that interact with Polkadot and Substrate chains. It connects through JSON-RPC providers, including smoldot light clients and WebSocket endpoints, and provides typed APIs for storage, constants, transactions, events, runtime calls and finalized blocks.

Explore the practical guide ↓

Independent OpenViST project profile, based on linked sources.

Polkadot API — OpenViST project profile in Developer Tools.
OpenViST project illustration. See the linked sources for product details.
Understand the project

Practical overview

When it fits

Use it when building a Polkadot or Substrate application that needs programmatic chain access through typed TypeScript APIs.

Who it is for

  • TypeScript developers building Polkadot or Substrate applications.
  • Teams that need typed access to chain data or application events.
  • Developers integrating browser-extension or private-key signers into transaction workflows.

Documented uses

  • Read typed chain storage and constants.
  • Subscribe to finalized blocks and events.
  • Access runtime calls and construct transaction workflows.
  • Connect an application through smoldot or a WebSocket RPC provider.
Before you choose

Requirements & limits

The public repository is licensed under MIT.

  • The README demonstrates both smoldot and WebSocket provider approaches; the selected endpoint and chain specification shape the connection.
  • Types and documentation are generated from on-chain metadata.
  • The libraries support browser-extension and private-key signers.
  • The package offers separate subpaths and dynamic imports to avoid bundling unnecessary assets and favor faster loading.

Check current requirements in the official documentation. Source-based guidance does not mean OpenViST has run or independently tested this project.

Source-based practical guide

Connect a client through smoldot

Set up the README’s light-client-backed JSON-RPC provider and create a Polkadot API client.

Before you start

  • A TypeScript application environment with the Polkadot API and smoldot packages available.
  • A worker-capable build setup for the README’s recommended smoldot Worker approach.
  • The Polkadot chain specification used by the example.

Steps

  1. Start smoldot with startFromWorker and a smoldot Worker.

  2. Dynamically import the Polkadot chain specification and add it to smoldot.

  3. Pass the resulting chain to getSmProvider to obtain a JSON-RPC provider.

  4. Pass that provider to createClient.

Expected outcome

A client connected through a smoldot light-client-backed provider.

Guide limitations

  • The README presents this setup for a Polkadot relay-chain specification; it does not establish compatibility with every chain.
  • The example documents connection setup, not a tested deployment or a guarantee of endpoint or chain availability.
Documentation 1 ↗
Evidence and transparency

Sources & review

Official repository ↗
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Sources checked
11 October 2026
Original website title
polkadot-api/polkadot-api · Official homepage title · retained in its source language
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