vercel/satori

Satori: Enlightened library to convert HTML and CSS to SVG.

Note

To use Satori in your project to generate PNG images like Open Graph images and social cards, check out our announcement and Vercel’s Open Graph Image Generation →

To use it in Next.js, take a look at the Next.js Open Graph Image Generation template →

Overview

Satori supports the JSX syntax, which makes it very straightforward to use. Here’s an overview of the basic usage:

// api.jsx
import satori from 'satori'

const svg = await satori(
  <div style={{ color: 'black' }}>hello, world</div>,
  {
    width: 600,
    height: 400,
    fonts: [
      {
        name: 'Roboto',
        // Use `fs` (Node.js only) or `fetch` to read the font as Buffer/ArrayBuffer and provide `data` here.
        data: robotoArrayBuffer,
        weight: 400,
        style: 'normal',
      },
    ],
  },
)

Satori will render the element into a 600×400 SVG, and return the SVG string:

'<svg ...><path d="..." fill="black"></path></svg>'

Under the hood, it handles layout calculation, font, typography and more, to generate a SVG that matches the exact same HTML and CSS in a browser.

Documentation

JSX

Satori only accepts JSX elements that are pure and stateless. You can use a subset of HTML elements (see section below), or custom React components, but React APIs such as useState, useEffect, dangerouslySetInnerHTML are not supported.

Experimental: builtin JSX support

Satori has an experimental JSX runtime that you can use without having to install React. You can enable it on a per-file basis with @jsxImportSource pragmas. In the future, it will autocomplete only the subset of HTML elements and CSS properties that Satori supports for better type-safety.

/** @jsxRuntime automatic */
/** @jsxImportSource satori/jsx */

import satori from 'satori';
import { FC, JSXNode } from 'satori/jsx';

const MyComponent: FC<{ children: JSXNode }> = ({ children }) => (
  <div style={{ color: 'black' }}>{children}</div>
)

const svg = await satori(
  <MyComponent>hello, world</MyComponent>,
  options,
)

Use without JSX

If you don't have JSX transpiler enabled, you can simply pass React-elements-like objects that have type, props.children and props.style (and other properties too) directly:

await satori(
  {
    type: 'div',
    props: {
      children: 'hello, world',
      style: { color: 'black' },
    },
  },
  options
)

HTML Elements

Satori supports a limited subset of HTML and CSS features, due to its special use cases. In general, only these static and visible elements and properties that are implemented.

For example, the <input> HTML element, the cursor CSS property are not in consideration. And you can't use <style> tags or external resources via <link> or <script>.

Also, Satori does not guarantee that the SVG will 100% match the browser-rendered HTML output since Satori implements its own layout engine based on the SVG 1.1 spec.

You can find the list of supported HTML elements and their preset styles here.

Images

You can use <img> to embed images. However, width, and height attributes are recommended to set:

await satori(
  <img src="https://picsum.photos/200/300" width={200} height={300} />,
  options
)

When using background-image, the image will be stretched to fit the element by default if you don't specify the size.

If you want to render the generated SVG to another image format such as PNG, it would be better to use base64 encoded image data (or buffer) directly as props.src so no extra I/O is needed in Satori:

await satori(
  <img src="data:image/png;base64,..." width={200} height={300} />,
  // Or src={arrayBuffer}, src={buffer}
  options
)

CSS

Satori uses the same Flexbox layout engine as React Native, and it’s not a complete CSS implementation. However, it supports a subset of the spec that covers most common CSS features:

Note:

1. Three-dimensional transforms are not supported.
2. There is no z-index support in SVG. Elements that come later in the document will be painted on top.
3. calc isn't supported.
4. currentColor support is only available for the color property.
5. CSS variables (custom properties) are supported, including inheritance, fallback values, and nested variables.

Language and Typography

Advanced typography features such as kerning, ligatures and other OpenType features are not currently supported.

RTL languages are not supported either.

Fonts

Satori currently supports three font formats: TTF, OTF and WOFF. Note that WOFF2 is not supported at the moment. You must specify the font if any text is rendered with Satori, and pass the font data as ArrayBuffer (web) or Buffer (Node.js):

await satori(
  <div style={{ fontFamily: 'Inter' }}>Hello</div>,
  {
    width: 600,
    height: 400,
    fonts: [
      {
        name: 'Inter',
        data: inter,
        weight: 400,
        style: 'normal',
      },
      {
        name: 'Inter',
        data: interBold,
        weight: 700,
        style: 'normal',
      },
    ],
  }
)

Multiple fonts can be passed to Satori and used in fontFamily.

[!TIP] We recommend you define global fonts instead of creating a new object and pass it to satori for better performance, if your fonts do not change. Read it for more detail

Emojis

To render custom images for specific graphemes, you can use graphemeImages option to map the grapheme to an image source:

await satori(
  <div>Next.js is 🤯!</div>,
  {
    ...,
    graphemeImages: {
      '🤯': 'https://cdnjs.cloudflare.com/ajax/libs/twemoji/14.0.2/svg/1f92f.svg',
    },
  }
)

The image will be resized to the current font-size (both width and height) as a square.

Locales

Satori supports rendering text in different locales. You can specify the supported locales via the lang attribute:

await satori(
  <div lang="ja-JP">骨</div>
)

Same characters can be rendered differently in different locales, you can specify the locale when necessary to force it to render with a specific font and locale. Check out this example to learn more.

Supported locales are exported as the Locale enum type.

Dynamically Load Emojis and Fonts

Satori supports dynamically loading emoji images (grapheme pictures) and fonts. The loadAdditionalAsset function will be called when a text segment is rendered but missing the image or font:

await satori(
  <div>👋 你好</div>,
  {
    // `code` will be the detected language code, `emoji` if it's an Emoji, or `unknown` if not able to tell.
    // `segment` will be the content to render.
    loadAdditionalAsset: async (code: string, segment: string) => {
      if (code === 'emoji') {
        // if segment is an emoji
        return `data:image/svg+xml;base64,...`
      }

      // if segment is normal text
      return loadFontFromSystem(code)
    }
  }
)

Runtime Support

Satori can be directly used in browser, Node.js (>= 16), and Web Workers. It bundles its underlying WASM dependencies as base64-encoded strings and loads them at runtime.

If there is a limitation on dynamically loading WASM (e.g. Cloudflare Workers), you can use the Standalone Build which is mentioned below.

Standalone Build of Satori

Satori's standalone build doesn't include Yoga's WASM binary by default, and you need to load it manually before using Satori.

First, you need to download the yoga.wasm binary from Satori build and provide it yourself. Let's use fetch to load it directly from the CDN as an example:

import satori, { init } from 'satori/standalone'

const res = await fetch('https://unpkg.com/satori/yoga.wasm')
const yogaWasm = await res.arrayBuffer()

await init(yogaWasm)

// Now you can use satori as usual
const svg = await satori(...)

Of course, you can also load the yoga.wasm file from your local disk via fs.readFile in Node.js or other methods.

Font Embedding

By default, Satori renders the text as <path> in SVG, instead of <text>. That means it embeds the font path data as inlined information, so succeeding processes (e.g. render the SVG on another platform) don’t need to deal with font files anymore.

You can turn off this behavior by setting embedFont to false, and Satori will use <text> instead:

const svg = await satori(
  <div style={{ color: 'black' }}>hello, world</div>,
  {
    ...,
    embedFont: false,
  },
)

Pixel Grid Rounding

Set pointScaleFactor to control how layout values are rounded to the pixel grid. This parameter is passed directly to Yoga’s pointScaleFactor and improves rendering precision on high-DPI displays.

const svg = await satori(
  <div style={{ color: 'black' }}>hello, world</div>,
  {
    ...,
    pointScaleFactor: 2,
  },
)

Debug

To draw the bounding box for debugging, you can pass debug: true as an option:

const svg = await satori(
  <div style={{ color: 'black' }}>hello, world</div>,
  {
    ...,
    debug: true,
  },
)

Contribute

You can use the Vercel OG Image Playground to test and report bugs of Satori. Please follow our contribution guidelines before opening a Pull Request.

Author

• Shu Ding (@shuding)