Svelte DevTools

A zero-config Vite plugin that injects a floating devtools panel into your Svelte 5 or SvelteKit app during development. Inspect routes, hover-highlight components in the DOM tree, and track runes state — all without leaving the browser. Drop-in setup, nothing included in production builds.

Features

• Routes Tab — current route ID, URL, status code, route params, and page data from load()
• Components Tab — live DOM tree with hover-to-highlight; click to expand/collapse subtrees
• State Tab — SvelteKit page store + any component runes state you opt in to expose
• Resizable bottom or right drawer, position persisted across reloads
• Keyboard shortcut ⇧ + ⌥ + D / Shift + Alt + D to toggle open/close

Installation

SvelteKit

npm install -D @svelte-devtools/vite-plugin @svelte-devtools/kit

vite.config.ts

import { defineConfig } from 'vite';
import { sveltekit } from '@sveltejs/kit/vite';
import { svelteDevtools } from '@svelte-devtools/vite-plugin';

export default defineConfig({
  plugins: [sveltekit(), svelteDevtools()],
});

src/hooks.server.ts

import { sequence } from '@sveltejs/kit/hooks';
import { svelteDevtoolsHandle } from '@svelte-devtools/kit';

export const handle = sequence(svelteDevtoolsHandle);

The SvelteKit handle is required because SvelteKit's SSR bypasses Vite's transformIndexHtml. The handle injects the devtools script tag via transformPageChunk instead.

Vite + Svelte (no SvelteKit)

npm install -D @svelte-devtools/vite-plugin

vite.config.ts

import { defineConfig } from 'vite';
import { svelte } from '@sveltejs/vite-plugin-svelte';
import { svelteDevtools } from '@svelte-devtools/vite-plugin';

export default defineConfig({
  plugins: [svelte(), svelteDevtools()],
});

No handle hook needed — the script is injected via transformIndexHtml.

Exposing component state

The State tab automatically shows the SvelteKit page store. To also display local runes state from a component, push it to window.__sdt inside a $effect:

$effect(() => {
  (window as any).__sdt.componentState = { count, name };
  window.dispatchEvent(new CustomEvent('__sdt:update', { detail: { type: 'state' } }));
});

The devtools panel will pick this up and display it under Component State alongside the page store.

Options

svelteDevtools() currently takes no configuration — just call it with no arguments. Options will be added in a future release.

Keyboard shortcut

The toggle button is always visible as a pill at the bottom center of the page.

Development

# 1. Clone and install
git clone https://github.com/chrislentz/svelte-devtools.git
cd svelte-devtools
npm run setup          # installs deps + builds the overlay bundle

# 2. Start the playground
npm run dev            # http://localhost:3001

# 3. Rebuild the overlay after making changes
npm run build:overlay  # or: npm run dev:overlay (watch mode, use alongside npm run dev)

Monorepo structure

packages/
  overlay/       — Svelte 5 panel UI (pre-built to dist/overlay.js, not published)
  vite-plugin/   — published as @svelte-devtools/vite-plugin
  kit/           — published as @svelte-devtools/kit
playground/      — SvelteKit sandbox for manual testing

Contributing

See CONTRIBUTING.md.

License

MIT © Chris Lentz