Msg#: 4628904 posted 2:43 am on Dec 11, 2013 (gmt 0)
:: detour to raw logs ::
Occurrences of "gzip" anywhere in logs within this calendar year:
6 January 22.214.171.124 - - <snip> "http://translate.google.com/translate_p<snip>" "Mozilla/5.0 (iPhone; CPU iPhone OS 6_0 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10A403 Safari/8536.25,gzip(gfe)"
19 February (unedited) * 126.96.36.199 - - [19/Feb/2013:23:44:53 -0800] "GET /games/LucysDownloads.html HTTP/1.1" 200 5522 "-" "Mozilla/5.0 (Windows NT 5.1; rv:19.0) Gecko/20100101 Firefox/19.0,gzip(gfe)" (Surrounding requests point to Translate, though referer didn't say so.)
14 March: two occurrences of 74.125.189.nnn
... Well, this is getting boring ;) In June for variety's sake we move to a 66.249.aa.bb IP. Further detour to 2012 confirms impression that they changed their default IP from 74.125 to 66.249 about six months ago. Now, obviously I've got a tiny little site-- but I don't see any occurrence of the element "gzip" in UAs other than Google Translate.
Some people also look at the X-Forwarded-For header-- either its content, or whether it exists at all. I know Google Preview sends one while Bing Preview (which is probably not a preview) doesn't. My second-to-last Translate request came with an X-Forwarded-For. Also a "Via:" header, if anyone cares.
In the specific case of google, you'll also see the element "translate" in the referer for non-page files. But that's after-the-fact information, unless you've also got hotlinking issues.
* Looking at this again, I really hope that google translate successfully rendered "for Macintosh only". I seriously doubt your average Windows system comes with a Mac Classic OS emulator.