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4.3.1 • Public • Published


Use the web3.js library as a collection of readable Svelte stores for Svelte or SvelteKit.

If you prefer to use the ethers.js library to intereact with EVM, you may be interested by our sister package svelte-ethers-store.


For additional help or discussion, join us in our Discord.


  1. add the svelte-web3 package
npm i svelte-web3
  1. add the web3.js library in the main HTML page (index.html in Svelte, src/template.html in Sapper or src/app.html in SvelteKit)
<script src=""></script>

This step is necessary for now because the Web3.js library doesn't play well with bundlers (Vite, Rollup, Webpack, Snowpack, etc), thus we cannot simply add a dependency in package.json.

Basic usage (default stores connected to one chain)

Derived stores

This library creates a set of readable Svelte stores that are automatically updated when a new connection happens, or when the chain or the selected account change. You can import them directly in any Svelte or JavaScript files :

import {
} from 'svelte-web3'
  • connected: store value is true if a connection has been set up.
  • web3: store value is a Web3.js instance when connected.
  • selectedAccount: store value is the current selected account (when connected).
  • chainId: store value is the current chainId when connected.
  • chainData: store value is the current blockchain CAIP-2 data (when connected), see below.

For these stores to be useful in your Svelte application, a connection to an EVM blockchain first need to established . The abstract helper defaultEvmStores can be used to initiate the connection and automatically instantiate all stores.

import { defaultEvmStores } from 'svelte-web3'

defaultEvmStores was named before defaultChainStore. The former naming has been removed in later versions of svelte-web3 package.

Connection with the browser provider (eg wallets like MetaMask)

To enable a connection with the current EIP-1193 provider injected in the browser window context, simply call setProvider on the library abstract helper with no argument:


Please note that setProvider can only to be called with no argument in a browser context. So you may want to use onMount when using Sapper or SvelteKit. Similarly, you cannot use setProvider with no argument in SSR context.

onMount(() => {
  // add a test to return in SSR context

svelte-web3 will automatically update the stores when the network or accounts change and remove listeners at disconnection.

previous version of svelte-web3 were using a special method setBrowserProvider. The former naming still works but will be removed in later versions. Please update your code!

Connection with non injected EIP-1193 providers

To connect to non injected EIP-1193 providers like :

  • web3-onboard
  • ethers.js
  • eth-provider
  • WalletConnect
  • Web3Modal

Call setProvider on the library abstract helper with the JavaScript provider instance object of the library. For example with Web3Modal :

const web3Modal = new Web3Modal(<your config>)
const provider = await web3Modal.connect()

svelte-web3 will automatically update the stores when the network or accounts change and remove listeners at disconnection.

Please check examples/svelte-app-template-web3/src/Web3Modal.svelte( in github for a complete example.

Connection with other Web3 providers (ws, http, ipc, ...)

Any provider supported by Web3.js can also be used with setProvider. A WS or HTTP RPC string URL or any providers returned by new Web3.providers, for example :

// or
// or
// or
  new Web3.providers.WebsocketProvider('ws://localhost:8546')
// or
var net = require('net')
  new Web3.providers.IpcProvider('/Users/myuser/Library/Ethereum/geth.ipc', net)
// etc...

Selecting a specific account

You can also pass Index as the second argument of setProvider() to select another account than the default when possible.

defaultEvmStores.setProvider(<provider>, <Index>)

Using the stores

After a connection has been established, you may import the stores anywhere in your application. Most of the time, you should use the $ prefix Svelte notation to access the stores values.

  import { connected, chainId } from 'svelte-web3'

{#if !$connected}

<p>My application is not yet connected</p>


<p>Connected to chain with id {$chainId}</p>


Using the Web3 API

Likewise use the $ prefix Svelte notation to access its instance and use the full Web3.js API. (beware, in the Web3.js library documentation, instances are always noted as web3, without $, but in the context of svelte-web3, web3 is the Svelte store itself, not it's value).

  import { web3, selectedAccount } from 'svelte-web3'

  // ...

  const { name, chainId } = await $web3.eth.getChainId()

  const balance = await $web3.eth.getBalance('0x0000000000000000000000000000000000000000') : ''

Using the contracts store for reactive contract calls

To enjoy the same reactivity as using $web3 but with a web3.eth.Contract contract instance, you first need to declare its address and interface. To differentiate each eth.Contract instance, you also need to define a logical name. That's the function attachContract:


  import { defaultEvmStores as evm } from 'svelte-web3'

  // ...

  evm.attachContract('myContract',<address>, <abi>)

attachContract only needs to be called once and can be called before connection since web3.eth.Contract instances will only be created when a connection becomes available. You may want to reattach new contract definition or abi for example when you the current network change. For the old definition will be overwritten and instance updated in the contracts store, simply use the same logical name.

After a contract as be declared, you can use its instance anywhere using the $ notation and the logical name :

  import { contracts } from 'svelte-web3'

  // ...

{#await $contracts.myContract.methods.totalSupply().call()}


{:then value}

<span>result of contract call totalSupply on my contract : { value } </span>


By default, svelte-web3 build contract instances using the current connection options. You may want to overwrite options by passing them as fourth argument.

  defaultEvmStores.attachContract('myContract', <address>, <abi>, { from: <account>, ... })

Reading stores outside of Svelte files

The $ prefix Svelte notation to access store values is only available inside Svelte files. To directly access the instantiated values in pure javascript library without subscribing to the store, you can use a special getter on the library abstract helper:

// this is not a Svelte file but a standard JavaScript file
import { defaultEvmStores } from 'svelte-web3'

if (defaultEvmStores.$selectedAccount) {
  // do something if store selectedAccount is non null

Forcing a disconnect (and removing all listeners)

Simply call the function disconnect directly on the on the library abstract helper:


Human readable chain CAIP-2 information

chainData is a store returning the current JavaScript CAIP-2 representation object.


The information returned by the chainData store depends (like all other web3 stores) on which chain the current provider is connected. If the store has not yet been connected (with setProvider), the store value will be undefined.

This object is extremely useful to build components that reactively update all variables elements that depends on the current active chain or account.

Below is the CAIP-2 formatted information when the default store is connected with the Ethereum Mainnet :

  "name": "Ethereum Mainnet",
  "chain": "ETH",
  "icon": "ethereum",
  "rpc": [
  "faucets": [],
  "nativeCurrency": {
    "name": "Ether",
    "symbol": "ETH",
    "decimals": 18
  "infoURL": "",
  "shortName": "eth",
  "chainId": 1,
  "networkId": 1,
  "slip44": 60,
  "ens": { "registry": "0x00000000000C2E074eC69A0dFb2997BA6C7d2e1e" },
  "explorers": [
      "name": "etherscan",
      "url": "",
      "standard": "EIP3091"

You might want to access all chains CAIP-2 data directly without using the chainData store. In this case, use the getter allChainsData, it returns the list of all CAIP-2 data available.

import { allChainsData } from 'svelte-web3'


Another solution is to use the helper function getChainDataByChainId that takes the chainId as argument and returns the CAIP-2 data or an empty object if not found.

import { getChainDataByChainId } from 'svelte-web3'


Web3 Svelte components

web3-svelte includes several basic Svelte components designed to simplify common tasks when building Ethereum-based applications. These components demonstrate how to use the web3-svelte library effectively and serve as reusable and composable best practices components. Currently, the library includes Balance, Identicon, and Jazzicon components. We encourage community members to contribute and help develop additional components by joining our discussions in our Discord.

You can find example usage of these components in the components route in the examples/sveltekit-app-template-web3 directory.

Balance Component

The Balance component displays the balance of a specified Ethereum address. To use the Balance component, import it and pass the address as a prop:

  import { Balance } from 'web3-svelte/components'

<p>Balance: <Balance address="0x0000000000000000000000000000000000000000" /></p>

Identicon Component

The Identicon component generates a unique identicon (a visual representation of an Ethereum address) using the ethereum-blockies-base64 library. To use the Identicon component, import it and pass the address as a prop:

  import { Identicon } from 'web3-svelte/components'

<Identicon address="0x0000000000000000000000000000000000000000" />

Jazzicon Component

The Jazzicon component generates a unique and colorful identicon using the @metamask/jazzicon library. To use the Jazzicon component, import it and pass the address and size (optional) as props:

  import { Jazzicon } from 'web3-svelte/components'

<Jazzicon address="0x0000000000000000000000000000000000000000" size="{32}" />

These components serve as a starting point for building your Ethereum-based applications using web3-svelte. You can further customize them and create additional components according to your application's requirements. By leveraging the reactivity and simplicity of Svelte along with the powerful features of web3.js, you can create a seamless and efficient user experience for your decentralized applications.

Simultaneous multi chain usage

You can also using the library to create several stores, each connected to different providers. For example, you may want a connection to the same chain througth the browser wallet and simultaneously with Infura; or many stores each connected to a different chains at the same time.

In this case, use the makeEvmStores factory function as below :

import { makeEvmStores } from 'svelte-web3'

let evmStores, web3, connected, selectedAccount, chainId, chainData
;({ web3, connected, selectedAccount, chainId, chainData, ...evmStores } =


<id> can be an arbitrary name to be able to retrieve the store with the function getChainStore without reinitializing the conection:

import { getChainStore } from 'svelte-web3'

let evmStores, web3, connected, selectedAccount, chainId, chainData
;({ web3, connected, selectedAccount, chainId, chainData, ...evmStores } =

The web3 store and all other derived stores will work the same way as with the default store.

If you want to use the different chain stores in the same Svelte file (not advised, it's better to use subcomponents), you may renamed the stores this way :

let evmStores_A, web3_A, evmStores_B, web3_B
;({ web3: web3_A, ...evmStores_A } = makeEvmStores('<id_A>'))(
  ({ web3: web3_B, ...evmStores_B } = makeEvmStores('<id_B>'))


What would be the most basic scaffolding to get Svelte + web3 running

Assuming that you already have a working injected provider like MetaMask in your browser:

  1. npm create vite@latest myapp -- --template svelte
  2. cd myapp && npm install svelte-web3
  3. add web3.js script loading tag inside the index.html header (see above)
  4. add this minimal connection code in App.svelte:
import { onMount } from 'svelte'
import { defaultEvmStores as evm, selectedAccount, chainId } from 'svelte-web3'
  1. use the stores in the HTML
<p>account: {$selectedAccount} / chainId: {$chainId}</p>
  1. npm run dev

X doesn't work after await defaultEvmStores.setProvider()

It's not sufficient to await for the setProvider to be certain that other derived stores have been populated. Instead you should subscribe to the needed store and put your code inside the handler.

For example:


import { defaultEvmStores as evm, web3, selectedAccount } from 'svelte-web3'

selectedAccount.subscribe(async ($selectedAccount) => {
  if (!$selectedAccount) return
  // do stuff here
  // ...

onMount(() => {

how to auto-connect on page load?

It is out of scope of this package to implement this function but it generally depends on the type of provider you are using and a way to store connection information between page loads (for example by using localStorage).


If you are using svelte-web3 to build an open source Dapp, let us know if you want to be listed in this section.

Svelte basic example (using Vite)

Please check examples/svelte-vite-template-web3 on github.

SvelteKit basic example

Please check examples/sveltekit-app-template-web3 on github.

Svelte basic example (based on rollup template)

This is a legacy example and will be removed in future version of svelte-web3.

Please check examples/svelte-app-template-web3 on github.

Contains demos to use the default store and multi stores.

Sapper basic example (based on webpack template)

This is a legacy example and will be removed in future version of svelte-web3.

Please check examples/sapper-app-template-web3 on github. presented at EthLisbon 2021

A website presented in EthLisbon 2021, used svelte-web3 (version 2) for building the frontend. :

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