If anyone is thinking of buying the 8GB version of the Sony Xperia M4 Aqua, then we wanted to make you fully aware that the handset will be severely limited when it comes to internal storage. Whilst the handset is marketed as having 8GB of internal storage, the amount of free space you actually get out of the box is around 1.25GB
Around 5GB of space is taken up by Android 5.0 Lollipop itself and another 2GB is taken up by pre-installed apps. Of course you might be thinking, you could free up quite a lot of memory by uninstalling various unwanted apps. But the issue here is that you wont be able to uninstall many of them as they are set as default apps and at best you can just disable them. Then again it wouldn’t really help you free up memory either. Some apps like Facebook etc can be deleted and you can get around 1.7GB of free storage but even that is less in our opinion.
European E2303 retail model of the Xperia M4 Aqua, which is SIM free so should have less bloatware than carrier versions. It is running firmware build 26.1.A.1.100 and the screenshots you see below are straight out of the box without installing any new apps. You can see that out of 8GB of storage, 4GB is taken up by Android 5.0 and just over 2GB of pre-installed apps. For our model, this leaves a paltry 1.26GB for our own apps, media, photos and videos.
Source