Eleventy-plugin-og-image NPM

Eleventy Plugin OG Image

This plugin helps to create Open Graph images in Eleventy using a template language of your choice^1 and CSS^3 via satori. No headless browser will be harmed 😉.

Usage

Install the package:

npm install eleventy-plugin-og-image --save-dev

Add the plugin to your .eleventy.js:

const EleventyPluginOgImage = require('eleventy-plugin-og-image');

module.exports = (eleventyConfig) => {
  eleventyConfig.addPlugin(EleventyPluginOgImage, {
    satoriOptions: {
      fonts: [
        {
          name: 'Inter',
          data: fs.readFileSync('../path/to/font-file/inter.woff'),
          weight: 700,
          style: 'normal',
        },
      ],
    },
  });
};

Create an OG-image-template, using the supported HTML elements^2 and CSS properties^3. CSS in <style> tags will be inlined, remote images fetched. This is an example og-image.og.njk:

<style>
    .root {
        width: 100%;
        height: 100%;
        display: flex;
        flex-direction: column;
        align-items: center;
        background: linear-gradient(135deg, #ef629f, #eecda3);
    }

    .title {
        color: white;
        font-size: 80px;
        margin: auto 0;
    }
</style>

<div class="root">
    <h1 class="title">{{ title }}</h1>
</div>

Call the ogImage shortcode inside the <head> in a template. The first argument is the filePath of the OG-image-template (required), second argument is for data (optional). Usage example in Nunjucks, e.g. example-page.njk:

{% ogImage "./og-image.og.njk", { title: "Hello World!" } %}

Result

Generated OG image _site/og-images/s0m3h4sh.png:

Generated OG image

HTML output generated by the shortcode in _site/example-page/index.html (can be modified via the generateHTML option):

<meta property="og:image" content="/og-images/s0m3h4sh.png" />

For applied usage see the example.

Note The template language of the page and OG-image-template can be mixed and matched.^1

Configuration

The following options can be passed when adding the plugin:

Property	Type	Default
`inputFileGlob`	`glob`	`*/.og.*`	This must match the OG-image-templates to prevent HTML compilation.
`getOutputFileSlug`	`function`	See source	Generation of the output file slug. Return must be url safe and exclude the file extension.
`outputFileExtension`	sharp output file formats	`png`
`outputDir`	`string`	`_site/og-images/`	Directory into which OG images will be emitted. Change `urlPath` accordingly.
`urlPath`	`string`	`/og-images/`	URL-prefix which will be used in returned meta-tags. Change `outputDir` accordingly.
`generateHTML`	`function`	See source	Change the rendered HTML in pages.
`satoriOptions`	satori options	`{ width: 1200, height: 630, fonts: [] }`	If an OG-image-template contains text, it's required to load a font (example).
`sharpOptions`	sharp output options	`undefined`	Options must be corresponding to chosen `outputFileExtension`.

Development Mode

During development the OG image file name is the url slug of the page it's generated from. In production builds, a hash of the content will be used. You'll have to handle this yourself, if you pass a custom getOutputFileSlug.

Advanced Usage

Custom Shortcode

If you would like to build your own shortcode, you can directly use the renderOgImage function.

const { renderOgImage } = require('eleventy-plugin-og-image/render');

const { html, svg, pngBuffer } = await renderOgImage({ inputPath, data, satoriOptions, templateConfig });

Capture Output URL

If you don't want to directly generate HTML with the shortcode, you can modify the generateHTML option to directly return the outputUrl:

eleventyConfig.addPlugin(EleventyPluginOgImage, {
  generateHTML: (outputUrl) => outputUrl,
});

Now you can capture the outputUrl in your page, e.g. in Nunjucks:

{% setAsync "ogOutputUrl" -%}
    {% ogImage "./og-image.og.njk", { title: "Hello World!" } %}
{%- endsetAsync %}

And use it anywhere below with {{ ogOutputUrl }}.

Acknowledgements & Attributions

This plugin is deeply inspired by @vercel/og.

Furthermore, it would not be possible without:

^1: Handlebars doesn't support async shortcodes and therefore can't use the ogImage shortcode. Nevertheless, an OG-image-template can use Handlebars (.og.hbs). ^2: Only a subset of HTML elements is supported by satori. ^3: Only a subset of CSS properties are supported by yoga-layout, which is used by satori.