I'm testing a webapp and found logentries that didn't make sense because I did not remember doing the requests. The remarkable thing is that they were all done using this useragent string
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.75 Safari/537.36 Google Favicon
In each case it only requested the main page and the favicon I defined.
Now the big difference with this question is that in my case the requests came from my own laptop (Ubuntu 16.4, Chrome 54). I know for sure it is my laptop because the logentry in the application server showed the full IPv6 address of my laptop. Today I tried the same with my Windows machine and the same happened. In fact: from my Windows machine the EXACT same useragent string was used including "(X11; Linux x86_64)"
The useragent string for the chrome I'm running is therfor completely different from what I see in those special requests.
What is really happening here?
My current suspicion is that Google Chrome itself does a request to bookmarked site to periodically update the stored favicon to shown on the bookmarks list. It seems to be a "special" part of chrome that apparently uses a 'fixed' useragent string indicating an older version of Chrome on Linux.