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FCL (Flow Client Library)

FCL is a TypeScript and JavaScript client library for Flow applications. It provides wallet discovery and authentication, wallet-authorized transactions, Cadence queries and transaction submission, plus utilities for reading account and network activity.

Explore the practical guide ↓

Independent OpenViST project profile, based on linked sources.

FCL (Flow Client Library) — 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 FCL when a JavaScript or TypeScript application needs a client integration for Flow wallet interactions, transaction submission or on-chain queries.

Who it is for

  • JavaScript and TypeScript developers building Flow dApps
  • Teams adding Flow wallet authentication or blockchain interactions to browser applications

Documented uses

  • Connect an application to FCL-compatible wallets and authenticate users.
  • Request wallet signatures and submit Flow transactions.
  • Run Cadence scripts to retrieve decoded on-chain results.
  • Retrieve account details and poll transaction status or events.
Before you choose

Requirements & limits

The project is open source under the Apache-2.0 license. Its README lists Node.js 12 or higher and installation through npm or Yarn. Dapper Wallet integration has a separate developer-account and setup requirement.

  • Wallet interactions are browser-only, although the library can also run in server environments.
  • Wallet support is described for FCL-compatible wallets.
  • The README's transaction example uses pre-1.0 Cadence syntax and directs developers to the migration guide for current syntax.

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

Add FCL to a JavaScript or TypeScript project

Install and import the FCL package as a starting point for Flow application integration.

Before you start

  • Node.js 12 or higher
  • An application project using JavaScript or TypeScript
  • npm or Yarn

Steps

  1. Install the @onflow/fcl package with npm or Yarn.

  2. Import it in an ES module with import * as fcl from "@onflow/fcl", or in Node.js with require("@onflow/fcl").

Expected outcome

The project has the FCL package available to use in its code.

Guide limitations

  • The installation instructions do not configure a wallet, network endpoint or application-specific transaction.
  • Wallet interaction is browser-only.
Documentation 1 ↗
Evidence and transparency

Sources & review

Official repository ↗
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Sources checked
10 October 2026
Original website title
onflow/fcl-js · Official homepage title · retained in its source language
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