Most popular variants of the header value (we only show this when there's just a bunch of variants):

• notranslate
• index,follow
• all,noodp,unavailable_after:Tuesday, 26-Feb-13 09…
• noindex, noindex, nofollow
• none, noindex, nofollow, noarchive
• noindex, nofollow, noindex, nofollow
• none;
• noindex, nofollow, nosnippet, noarchive, noimagei…
• Crawl-delay: 10
• noindex, nofollow, noindex, nofollow, nosnippet, …
• noimageindex
• noindex, nofollow, noarchive, none
• none, none
• noindex,noodp
• "noindex, nofollow"
• noodp,index,follow,noarchive
• noindex,follow
• nofollow, noindex, noarchive, noimageindex
• noindex, nofollow, noarchive, noindex, nofollow, …
• none, none, none
• noindex, noarchive, nosnippet, unavailable_after:…
• Googlebot: noindex, Googlebot-Image: noindex, Goo…
• noindex, noarchive, nosnippet
• : noindex,nofollow
• noodp
• noindex,nofollow
• index, archive
• "noindex"
• noindex, noindex, noindex
• all,noodp
• none
• none, none, none, none, none, none
• noarchive,nofollow,noimageindex,noindex,none,nood…
• noindex, noarchive, nosnippet, noimageindex, nood…
• noindex, noimageindex, follow
• noindex, noarchive, nosnippet, nofollow
• noindex, nofollow
• noindex, nofollow, noarchive, nosnippet, noodp
• noindex, nofollow, noarchive, noodp, noimageindex…
• none, noarchive, nofollow, noindex, nosnippet, no…
• no-index,no-follow
• noindex, follow
• noindex, nofollow, noarchive, nosnippet
• nofollow
• noarchive, noindex, nofollow
• index, follow, noarchive
• noindex,nofollow,noarchive
• all
• all, noimageindex
• index, noodp, noydir
• noindex,noarchive,nosnippet,follow
• noindex,noarchive,nofollow,nosnippet
• : None
• nofollow, noindex
• Noindex, Nofollow
• none, noarchive, nosnippet, noodp, notranslate, n…
• noindex, nofollow, nosnippet, noarchive
• noindex,nofollow,noarchive,nosnippet
• noindex, nofollow, noarchive, nosnippet, noodp, n…
• all,noimageindex,noodp
• index
• otherbot: noindex, nofollow, googlebot: noindex, …
• none, noarchive
• noarchive, noindex
• noindex, nofollow, noimageindex
• noindex, nofollow, noarchive, nocache, noimageind…
• NOINDEX
• noarchive,nofollow,noindex,nosnippet
• noarchive, nosnippet
• none, none, none, none, none
• noindex
• noindex, noindex
• no-index
• none, none, none, none
• noarchive, notranslate
• index, follow, archive, snippet
• noarchive
• noindex, nofollow, noarchive, noimageindex
• noindex, noarchive
• noindex, nofollow, noarchive
• noarchive, nosnippet, noindex, nofollow
• noimageindex,noodp
• nofollow, noindex, noarchive, nosnippet
• nofollow, noindex, noarchive
• unavailable_after: Sun, 22 Apr 2018 00:00:00 +0200
• noindex, noarchive, nofollow
• noimageindex, noindex
• index, nofollow, noarchive, nosnippet
• noindex,nofollow,noarchive,nosnippet,noydir,noodp
• noindex, nofollow, nocache, noarchive
• noindex,nofollow,none,noarchive,nosnippet,noodp,n…
• noarchive, noindex, nosnippet
• noindex,follow,noarchive
• noindex, nofollow, nosnippet
• index, follow
• all,noimageindex
• none, noindex, nofollow
• index, follow, noarchive, noodp

Controls the behavior of search engine bots and may contain most of the directives usually found in robots.txt file.

Reference...