What is the method of identifying if CSS supports webp images?

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One method of identifying if CSS supports webp images is by using the "image-set" function in CSS. The "image-set" function allows you to specify multiple images with different file formats and resolutions, and the browser will choose the most appropriate image to display based on the device's capabilities.

To use the "image-set" function with webp images, you can include the webp image as the first item in the image set, followed by a fallback image in a different format, such as JPEG or PNG. For example:

.my-image {
  background-image: -webkit-image-set(url('image.webp') 1x, url('image.jpg') 1x);
  background-image: image-set(url('image.webp') 1x, url('image.jpg') 1x);
}

This CSS code sets the background image of the ".my-image" element to be either the "image.webp" file or the "image.jpg" file, depending on whether the browser supports webp images. If the browser does not support webp, it will fall back to using the JPEG image instead.

You can also use JavaScript to detect if the browser supports webp images using the "Image" object and checking for its "onload" and "onerror" events. For example:

var img = new Image();
img.onload = function() {
  // webp is supported
};
img.onerror = function() {
  // webp is not supported
};
img.src = 'image.webp';