source - srcset

<source srcset="URL">

The srcset attribute specifies the URL of the image to use in different situations.

This attribute is required when <source> is used in <picture>.

Possible values:

• An absolute URL - points to another web site (like href="http://www.example.com/flower.jpg")
• A relative URL - points to a file within a web site (like href="flower.jpg")