snapDOM

snapDOM is a fast and accurate DOM-to-image capture tool built for Zumly, a zoom-based view transition framework.

It captures any HTML element as a scalable SVG image, preserving styles, fonts, background images, pseudo-elements, and even shadow DOM. It also supports export to raster image formats and canvas.

• 📸 Full DOM capture
• 🎨 Embedded styles, pseudo-elements, and fonts
• 🖼️ Export to SVG, PNG, JPG, WebP, or canvas
• ⚡ Ultra fast, no dependencies
• 📦 100% based on standard Web APIs

Demo

https://zumerlab.github.io/snapdom/

Installation

NPM / Yarn

npm i @zumer/snapdom

yarn add @zumer/snapdom

CDN

<script src="https://cdn.jsdelivr.net/npm/@zumer/snapdom/dist/snapdom.min.js"></script>

Script tag (local)

<script src="snapdom.js"></script>

ES Module

import { snapdom } from './snapdom.mjs';

Module via CDN

<script type="module">
  import { snapdom } from 'https://cdn.jsdelivr.net/npm/@zumer/snapdom/dist/snapdom.mjs';
</script>

Basic usage

Reusable capture

const el = document.querySelector('#target');
const result = await snapdom(el, { scale: 2 });

const img = await result.toPng();
document.body.appendChild(img);

await result.download({ format: 'jpg', filename: 'my-capture' });

One-step shortcuts

const el = document.querySelector('#target');
const png = await snapdom.toPng(el);
document.body.appendChild(png);

const blob = await snapdom.toBlob(el);

API

snapdom(el, options?)

Returns an object with reusable export methods:

{
  url: string;
  toRaw(): string;
  toImg(): Promise<HTMLImageElement>;
  toCanvas(): Promise<HTMLCanvasElement>;
  toBlob(): Promise<Blob>;
  toPng(): Promise<HTMLImageElement>;
  toJpg(options?): Promise<HTMLImageElement>;
  toWebp(options?): Promise<HTMLImageElement>;
  download(options?): Promise<void>;
}

Shortcut methods

Options

All capture methods accept an options object:

Cross-Origin Images

By default, snapDOM loads images with crossOrigin="anonymous". You can customize this behavior using the crossOrigin option:

const result = await snapdom(element, {
  crossOrigin: (url) => {
    // Use credentials for same-origin images
    if (url.startsWith(window.location.origin)) {
      return "use-credentials";
    }
    // Use anonymous for cross-origin images
    return "anonymous";
  }
});

This is useful when your images require authentication or when dealing with credentialed requests.

Download options

{
  format?: "svg" | "png" | "jpg" | "jpeg" | "webp"; // default: "png"
  filename?: string;         // default: "capture"
  backgroundColor?: string;  // optional override
}

preCache() – Optional helper

The preCache() function can be used to load external resources (like images and fonts) in advance. It is specially useful when the element to capure is big and complex.

import { preCache } from '@zumer/snapdom';

await preCache(document.body);

import { snapdom, preCache } from './snapdom.mjs';
    window.addEventListener('load', async () => {
    await preCache();
    console.log('📦 Resources preloaded');
    });

Options for preCache():

• embedFonts (boolean, default: true) — Inlines non-icon fonts during preload.
• reset (boolean, default: false) — Clears all existing internal caches.
• crossOrigin (function) — Function to determine CORS mode per image URL during preload.

Features

• Captures shadow DOM and Web Components
• Supports ::before and ::after pseudo-elements
• Inlines background images and fonts
• Handles Font Awesome, Material Icons, and more
• data-capture="exclude" to ignore an element
• data-capture="placeholder" with data-placeholder-text for masked replacements

Limitations

• External images must be CORS-accessible (use crossOrigin option for credentialed requests)
• Iframes are not supported
• When WebP format is used on Safari, it will fallback to PNG rendering.
• @font-face CSS rule is well supported, but if need to use JS FontFace(), see this workaround #43

Benchmarks

snapDOM is not only highly accurate — it’s extremely fast.

Latest benchmarks show significant performance improvements against other libraries:

Run the benchmarks

To run these benchmarks yourself:

git clone https://github.com/zumerlab/snapdom.git
cd snapdom
npm install
npm run test:benchmark

They execute in headless Chromium using real DOM nodes.

Contributors 🙌

License

MIT © Zumerlab