html2canvas

This project is a fork of niklasvh/html2canvas.

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JavaScript HTML renderer

The script allows you to take "screenshots" of webpages or parts of it, directly on the users browser. The screenshot is based on the DOM and as such may not be 100% accurate to the real representation as it does not make an actual screenshot, but builds the screenshot based on the information available on the page.

How does it work?

The script renders the current page as a canvas image, by reading the DOM and the different styles applied to the elements.

It does not require any rendering from the server, as the whole image is created on the client's browser. However, as it is heavily dependent on the browser, this library is not suitable to be used in nodejs. It doesn't magically circumvent any browser content policy restrictions either, so rendering cross-origin content will require a proxy to get the content to the same origin. You can pass a proxy URL via the proxy option — the proxy must accept a ?url= query parameter and return the resource as a base64 data URI.

Browser compatibility

The library works on all modern evergreen browsers:

• Firefox
• Chrome / Chromium-based browsers (Edge, Opera, …)
• Safari

As each CSS property needs to be manually built to be supported, there are a number of properties that are not yet supported.

Install

npm i @html2canvas/html2canvas
# yarn add @html2canvas/html2canvas
# pnpm add @html2canvas/html2canvas

Usage

To render an element with html2canvas, simply call: html2canvas(element[, options]);

The function returns a Promise containing the <canvas> element. Simply add a promise fulfillment handler to the promise using then:

html2canvas(document.body).then(function (canvas) {
    document.body.appendChild(canvas);
});

or

html2canvas(document.body).then(canvas => {
    document.body.appendChild(canvas);
});

or

const canvas = await html2canvas(document.body);
document.body.appendChild(canvas);

or with TypeScript:

import html2canvas from '@html2canvas/html2canvas';

const canvas = await html2canvas(document.body);
document.body.appendChild(canvas);

Building

You can download ready builds here.

Clone git repository:

git clone git://github.com/html2canvas/html2canvas.git

Install dependencies:

npm install

Build browser bundle:

npm run build

Testing

Unit tests (no browser required):

npm run unittest

Visual regression tests (Playwright):

The project uses Playwright to run visual regression tests against all reftest HTML fixtures. Each fixture is rendered through html2canvas and the output is compared pixel-by-pixel against committed baseline snapshots.

The tests run inside a Docker container so the rendering (fonts in particular) is reproducible and matches the committed baselines. Running Playwright directly against the host would depend on the system fonts and produce spurious diffs.

1. Run the visual regression tests (the container builds the project first):

   npm run test:visual:docker

2. If a test fails, open the interactive HTML report to inspect diffs:

   npm run test:visual:report

3. After an intentional rendering change, update the baselines:

   npm run test:visual:docker:update

   This regenerates all snapshot PNGs in tests/visual/reftests.spec.ts-snapshots/. Review the changes and commit them.

Legacy browser reftests (Karma):

1. Build the project, then start the local dev server:

   npm run build
   npm start

2. Open the test runner in your browser:

   http://localhost:8080/tests/testrunner.html

   Individual reftest pages (e.g. tests/reftests/background/box-shadow.html) can also be opened directly to inspect a specific feature.

Website

The website source lives in the www/ directory and is built with Astro. Documentation pages are Markdown files in docs/.

To run the website locally:

cd www
npm install
npm run dev

Examples

For more information and examples, please visit the homepage or try the test console.

Contributing

If you wish to contribute to the project, please send the pull requests to the develop branch. Before submitting any changes, try and test that the changes work with all the support browsers. If some CSS property isn't supported or is incomplete, please create appropriate tests for it as well before submitting any code changes.