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createFcl

Creates a configured FCL (Flow Client Library) core instance. This function initializes FCL with the core functionality needed to interact with the Flow blockchain, providing a complete interface for blockchain operations.

The created FCL instance includes all core functionality for:

  • User authentication and wallet connections
  • Transaction submission and monitoring
  • Blockchain queries and event subscriptions
  • Configuration management
  • Discovery service integration
  • SDK method access

This function automatically configures the HTTP transport and creates all necessary services and utilities. The transport parameter is optional and defaults to HTTP transport.

Import​

You can import the entire package and access the function:


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import * as fcl from "@onflow/fcl-core"
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fcl.createFcl(params)

Or import directly the specific function:


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import { createFcl } from "@onflow/fcl-core"
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createFcl(params)

Usage​


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// Basic FCL instance creation
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import { createFcl } from "@onflow/fcl-core"
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const fcl = createFcl({
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accessNodeUrl: "https://rest-testnet.onflow.org",
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computeLimit: 1000,
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flowNetwork: "testnet"
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})
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// Use the instance for authentication
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const user = await fcl.currentUser.authenticate()
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console.log("Authenticated user:", user.addr)
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// Submit a transaction
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const txId = await fcl.mutate({
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cadence: `
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transaction {
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execute { log("Hello, Flow!") }
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}
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`
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})
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// Query the blockchain
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const result = await fcl.query({
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cadence: `
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pub fun main(): Int {
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return 42
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}
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`
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})

Parameters​

params​

  • Type:

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WithOptionalProperties<FCLConfig, "transport">

  • Description: Configuration parameters for the FCL instance

Properties:​

  • accessNodeUrl - URL of the Flow access node (e.g., "https://rest-testnet.onflow.org")
  • computeLimit - Default compute limit for transactions and queries
  • customResolver - Optional custom resolver for address replacement
  • customDecoders - Optional custom decoders for response parsing
  • contracts - Optional contract address mappings
  • platform - Platform identifier (e.g., "web", "mobile", "extension")
  • discoveryWallet - Optional discovery wallet endpoint
  • discoveryWalletMethod - Optional discovery wallet method
  • defaultComputeLimit - Optional default compute limit override
  • flowNetwork - Optional Flow network identifier
  • serviceOpenIdScopes - Optional OpenID scopes for services
  • walletconnectProjectId - Optional WalletConnect project ID
  • walletconnectDisableNotifications - Optional flag to disable WalletConnect notifications
  • storage - Storage provider for session persistence
  • discovery - Optional discovery configuration with execStrategy
  • transport - Optional transport layer (defaults to HTTP transport)

Returns​

any

A fully configured FCL instance with all core methods and services including:

  • currentUser: User authentication and management service
  • config: Configuration management service
  • mutate: Transaction submission function
  • query: Blockchain query function
  • queryRaw: Raw blockchain query function
  • verifyUserSignatures: User signature verification
  • getChainId: Chain ID retrieval
  • tx: Transaction monitoring utilities
  • events: Event subscription utilities
  • authenticate: User authentication method
  • unauthenticate: User logout method
  • signUserMessage: Message signing method
  • All SDK methods (send, decode, subscribe, etc.)
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