This can be useful, for example if you wish to translate the pseudo class content texts (e.g. when using them for tooltips). Currently attr() is supported for content property and almost no browser supports it for other properties, but perhaps they will in the future. Furthermore, the values from attr() are strings, so it really was only meant to be used for content in the first place and can’t be used for units (e.g. font-size) or urls (e.g. content: url() ). Talking of which:
... read the whole story at medium.com.
This can be used for many types of media (image, sound, video).