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An extension that allows inspection of Svelte component hierarchy and state in the Firefox and Chrome developer tools.
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Svelte DevTools

Mozilla Add-on Chrome Web Store

Install from the Firefox addon page or the Chrome addon page

Svelte Devtools is a Firefox and Chrome extension for the Svelte javascript framework. It allows you to inspect the Svelte state and component hierarchies in the Developer Tools.

After installing you will see a new tab in Developer Tools. This tab displays a tree of Svelte components, HTMLx blocks, and DOM elements that were rendered on the page. By selecting one of the nodes in the tree, you can inspect and edit its current state in the panel to the right.

Requires svelte version 3.12.0 or above

1.1.0 Screenshot

Enabling dev mode

In order for svelte-devtools to comunicate with your application bundle the svelte compiler must have the dev option set to true.


By default the svelte template will set dev: true when running npm run dev and false otherwise.


Below is a minimalist rollup config with dev: true set.

// rollup.config.js
import * as fs from 'fs';
import svelte from 'rollup-plugin-svelte';

export default {
  input: 'src/main.js',
  output: {
    file: 'public/bundle.js',
    format: 'iife'
  plugins: [
      dev: true


Below is the relevant snipet from a webpack.config.js with dev: true set.

  module: {
    rules: [
        test: /\.(html|svelte)$/,
        exclude: /node_modules/,
        use: {
          loader: 'svelte-loader',
          options: {
            dev: true,

Build from source


Clone this repository and run the package script.

git clone
cd svelte-devtools
npm install
npm run package

This should build the codebase and output a zip file under web-ext-artifacts.



Unsigned addons can't be install in firefox permanently but addons can be installed temporarily.

  1. Navigate to about:debugging.
  2. Click "Load Temporary Add-on" and choose the generated zip file.


  1. Navigate to chrome://extensions/.
  2. Turn on developer mode using the 'Developer mode' switch in the upper right hand corner of the page.
  3. Click 'Load Unpacked' and select the dest directory.
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