Update: Based on Scott’s comment on the post I dug deeper. There are 2 settings that affect the UserAgent string on the fire: The “Accelerate page loading” and “Desktop or mobile view setting” (both under menu-> settings while in the browser)
Update: I made a simple javascript that can detect a Kindle Fire based on the existence of Silk/ and Silk-Accelerated in the UserAgent.
Is it a Kindle Fire?
Here’s the breakdown:
Mobile – no Silk
Mozilla/5.0 (Linux; U; Android 2.3.4; en-us; Silk/1.1.0-84) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1 Silk-Accelerated=false
Mobile – Silk
Mozilla/5.0 (Linux; U; Android 2.3.4; en-us; Silk/1.1.0-84) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1 Silk-Accelerated=true
Desktop – no Silk
Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-us; Silk/1.1.0-80) AppleWebKit/533.16 (KHTML, like Gecko) Version/5.0 Safari/533.16 Silk-Accelerated=false
Desktop – Silk
Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-us; Silk/1.1.0-80) AppleWebKit/533.16 (KHTML, like Gecko) Version/5.0 Safari/533.16 Silk-Accelerated=true
Automatic – no Silk
Either Mobile – no Silk or Desktop – no Silk (Depending on the site visited)
Automatic – Silk
Either Mobile – Silk or Desktop – Silk (Depending on the site visited)
Based on this, the best bet at marking Fire traffic is to search for Silk and/or Silk-Accelerated in the UA.

I started seeing a lot of traffic with a network named “amazon.com inc.” in my Google Analytics account, specifically to my Kindle Fire market opener post and apk. The browser data showed Mac OS X and Safari, I was puzzled until I figured out that the Fire pretends to be Safari on OSX 10.6.3 and shows amazon.com inc. as the network instead of the actual network. Is it an Amazon oversight or is there a reason for this? It kinda messes with trying to decipher how much kindle traffic you are getting. It’s got Silk references so it can be identified but, as far as I know, GA does not offer up the entire UA string.