Google being the largest threat to Apple with their Android OS has proven to be a heavyweight in the mobile arena. With this the Apple App Store and Google Play Market have hundreds of thousands of apps. Android however requires much more thought when it comes to app design since its popularity has created a demand for many different screen resolutions, custom UI’s, and hardware configurations. Android fragmentation is due to the number of manufacturers out there using Android for their mobile OS with many different devices.
While all developers have the intension of creating ideal experiences for every user having 4,000+ different models to test on is not at all ideal. You would need to develop different versions of your Android app many times to allow it to function on every device the way you intend it to. This being said the most popular devices can be tested and verified working but its unlikely you will ever be able to develop and Android app to work on every device.
iOS developers have it easy with only a couple different resolutions to deal with although most Android devices can be developed for by making sure it works for the 5 major screen resolutions so don’t let this hold you back. With every manufacturer wanting to design the new thing with the highest resolution and newest hardware its likely that Android fragmentation will get increasingly worse. This being said fragmentation is the future and will likely fall hand in hand with innovation.