Bad value for attribute “srcset” on element “img”: Ends with empty image-candidate string.

An srcset attribute must not end with a trailing comma, as each entry must be a complete image candidate string with a URL and an optional width or pixel density descriptor.

The srcset attribute accepts a comma-separated list of image candidate strings. Each string contains a URL and, optionally, a width descriptor (like 400w) or a pixel density descriptor (like 2x). A trailing comma after the last entry creates an empty image candidate string, which is invalid.

This error often appears when srcset values are built dynamically by a template engine or CMS that appends a comma after every item, including the last one.

Invalid example

<img
  srcset="image-small.jpg 400w,
          image-medium.jpg 800w,
          image-large.jpg 1200w,"
  sizes="(max-width: 800px) 400px, 800px"
  src="image-medium.jpg"
  alt="A sample photo"
>

The trailing comma after image-large.jpg 1200w, produces the validation error.

Fixed example

<img
  srcset="image-small.jpg 400w,
          image-medium.jpg 800w,
          image-large.jpg 1200w"
  sizes="(max-width: 800px) 400px, 800px"
  src="image-medium.jpg"
  alt="A sample photo"
>

Removing the trailing comma after the last image candidate string fixes the issue.

Learn more:

MDN Reference

HTML img element - srcset attribute

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MDN Reference

HTML Responsive Images

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WHATWG Spec

Images in HTML

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