svelte web3 is provider for web3.js for handle request network to metamask or other provider. Example see here.
Need Contribution For Better Docs
Use any package manager do you want.
// Using Yarn to install
yarn add --dev svelte-web3-provider
// or if you prefer NPM
npm install --save-dev svelte-web3-provider
You must add Web3Provider to root layout and Web3Provider will detect if browser support etehreum or not. if not, you can set fallback provider.So, it will use the provider you have set.
<script>
    // routes/+layout.svelte
    import Web3Provider from 'svelte-web3-provider';
    import net from 'net'
    import Web3 from 'web3'
</script>
    
<!--  No Fallback Provider -->
<Web3Provider />
<!--  With Fallback Provider -->
<Web3Provider fallbackProvider="http://localhost:8545" />
<Web3Provider fallbackProvider={new Web3.providers.WebsocketProvider('ws://localhost:8546')} />
<Web3Provider fallbackProvider={new Web3.providers.IpcProvider('/Users/myuser/Library/Ethereum/geth.ipc', net)} />
<slot/>
Then, you can do everything u need with web3.js. like this
<script>
// routes/auto/+layout.svelte
    import Web3Provider from '$lib';
</script>
<Web3Provider/>
<main>
    <slot />
</main>
<script>
    // routes/auto/+page.svelte
    import { connected, isLoading, isSupportEthereum, selectedAccount, web3 } from 'svelte-web3-provider';
    let balance = '';
    $: if ($web3 && $selectedAccount) {
        $web3.eth.getBalance($selectedAccount).then(value => {
            balance=value
        });
    }
</script>
<p>{$selectedAccount || 'no address'}</p>
<p>Balance: {balance}</p>
{#if $connected}
    Connected wallet
{:else}
    wallet not connected
{/if}
{#if $isLoading}
    <p>Loading...</p>
{/if}
{#if !$isSupportEthereum}
    <p>not support ethereum network</p>
{/if}
you can change your provider on the fly(example: change provider after 2 seconds). use setProvider
<script>
// routes/onthefly/+layout.svelte
    import Web3Provider from '$lib';
</script>
<Web3Provider/>
<main>
    <slot />
</main>
<script>
// routes/onthefly/+page.svelte
    import { browser } from '$app/environment';
    import {
        connected,
        isLoading,
        isSupportEthereum,
        selectedAccount,
        setProvider,
        web3
    } from '$lib';
    let balance = '';
    $: if (browser) {
        setTimeout(() => {
            // do like this
            setProvider('http://127.0.0.1:8545');
        }, 2000);
    }
    $: if ($web3 && $selectedAccount) {
        $web3.eth.getBalance($selectedAccount).then((value) => {
            balance = value;
        });
    }
</script>
<p>{$selectedAccount || 'no address'}</p>
<p>Balance: {balance}</p>
{#if $connected}
    Connected wallet
{:else}
    wallet not connected
{/if}
{#if $isLoading}
    <p>Loading...</p>
{/if}
{#if !$isSupportEthereum}
    <p>not support ethereum network</p>
{/if}
you have to set manual props in Web3Provider to disable detect automatically browser and do what you want
<script>
// routes/manual/+layout.svelte
    import Web3Provider from '$lib';
</script>
<Web3Provider manual/>
<main>
    <slot />
</main>
<script>
// routes/manual/+page.svelte
    import { browser } from '$app/environment';
    import {
        connected,
        isLoading,
        isSupportEthereum,
        selectedAccount,
        setProvider,
        web3
    } from '$lib';
    let balance = '';
    $: if (browser) {
        // set your provider like this
        // then, all store will reactivy automatically
        setProvider('http://127.0.0.1:8545');
    }
    $: if ($web3 && $selectedAccount) {
        $web3.eth.getBalance($selectedAccount).then((value) => {
            balance = value;
        });
    }
</script>
<p>{$selectedAccount || 'no address'}</p>
<p>Balance: {balance}</p>
{#if $connected}
    Connected wallet
{:else}
    wallet not connected
{/if}
{#if $isLoading}
    <p>Loading...</p>
{/if}
{#if !$isSupportEthereum}
    <p>not support ethereum network</p>
{/if}
u can see available store in this file