A high-performance, responsive image component for WebC.

Installation and usage

npm install @unpic/webc

The requires @11ty/webc version 0.9.0 or later, because it uses the new webc.attributes feature.

If you are using this with Eleventy, there are a number of ways of defining WebC components. In the example we’re using webc:import, but check out the docs for other options that handle imports automatically. You can then use the component in your templates:

  alt="A lovely bath"


The component accepts all the props of an <img> tag, plus the following:


The resizing behaviour of the image.

  • constrained: (default) the image will be rendered at a maximum of width and height, but will scale down automatically if the container is smaller, maintaining the aspect ratio.
  • fullWidth: the image will be rendered at full width of its container. This is optimized for full-width hero images. You can set height to a fixed value, which will mean the image will be rendered at that fixed height and scale horizontally to fill the container.
  • fixed: the image will be rendered at the exact size specified by width and height


By default, images are loaded lazily. If priority is set to true, the image will be loaded eagerly, and will be given high priority by the browser. This is useful for images that are above the fold, particularly large ones such as hero images.


Either an image URL, CSS gradient or CSS colour value. If set to auto, a low-resolution version of the image will be rendered as a background image, with a blurred placeholder effect. This is still loaded from the remote server, so if you can instead provide an inline base64-encoded version of the image or background colour, you should do that instead. Look at @unpic/placeholder for a library that can generate these placeholders.

Bear in mind that this is not removed after the image loads, so it will be visible if the image has transparency.


Instead of specifying both width and height, you can specify can aspectRatio.


By default the CDN is auto-detected from the src URL. If you want to override this, you can specify a CDN object. See the unpic for supported values.


By default the image breakpoints used in the srcset are generated based on the layout and image size. You can override this by specifying an array of breakpoints. The breakpoints are specified as an array of numbers, representing the width of the image in pixels.

Other props

Any prop supported by <img> tags can be passed in, except srcset which is generated from src. The following props are set automatically, but can be overridden if you need to:

  • sizes
  • role
  • decoding
  • loading
  • fetchpriority