Google has announced that it is going to update its user-agent of Googlebot for smartphones from iPhone to Android on 18 April 2016. Google has also added that this change will bring no impact on all websites (approximate up to 99%).
Have a look on the new Google user-agent for Smartphone which is Google is Going to update in the upcoming month of April on 18, 2016.
Mozilla/5.0 (Linux; Android 6.0.1; Nexus 5X Build/MMB29P) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.96 Mobile Safari/537.36 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
And also look at the below mentioned existing user-agent for Smartphone which is working currently for all websites on the web
Mozilla/5.0 (iPhone; CPU iPhone OS 8_3 like Mac OS X) AppleWebKit/600.1.4 (KHTML, like Gecko) Version/8.0 Mobile/12F70 Safari/600.1.4 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
The Major difference which is clearly visible from the above mentioned user-agent string is that Google is substituting Apple iPhone and Safari string with Chrome and Android.
According to Google, Google is doing these changes in order to better understand the latest technologies which webmasters are using for their websites as Web is developing and therefore Google has decided to make a change in the user-agent string.
Thus in order to check that your site is not got affected by this change of Google, make use of Google’s Fetch and Render Tool in Google Search Console (Google Web Master).