Underscores or hyphens in the urls of images?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Rad Paluszak: If it was about solely URLs, I would say go for black-cats. However the content of images is determined by the alt attributes, surrounding text and other. If, however, URLs are suggested to be construed using hyphens, then I`d stick to that.

• This answer was selected as Best Community Answer by the Expert Panel

  
  Alan Bleiweiss: While you can use either, as both are valid for SEO overall, using underscores in URLs is not a best practice for accessibility reasons, in that a URL with an underscore that is also underlined, can, in some narrow situations, cause people to fail to realize there`s an underscore. It`s a minor, nearly insignificant issue, however it exists, and thus, since I happen to live in maximized best practices, I prefer to not use the underscore.
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  Neil Cheesman: For info... 5 years ago... (I knew I had seen this somewhere) Matt Cutts explains the difference between how Google interprets underscores and dashes in a URL. https://youtu.be/AQcSFsQyct8