robots.txt disallow google bot on root domain but allow google image bot?

Question

Would having the following robot.txt work?

User-agent: *
Disallow: /

User-agent: Googlebot-Image
Allow: /

My idea is to avoid google crawling my cdn domain but allowing google image still crawl and index my images.

Answer 1

The file has to be called robots.txt, not robot.txt.

Note that User-agent: * targets all bots (that are not matched by another User-agent record), not only the Googlebot. So if you want allow other bots to crawl your site, you would want to use User-agent: Googlebot instead.

So this robots.txt would allow "Googlebot-Image" everything, and disallow everything for all other bots:

User-agent: Googlebot-Image
Disallow:

User-agent: *
Disallow: /

(Note that Disallow: with an empty string value is equivalent to Allow: /, but the Allow field is not part of the original robots.txt specification, although some parsers support it, among them Google’s).