Help Can't Transfer Data. Why?

[AgentCPU0]

For pretty much all Android devices, we have 3 options to save our apps to. Our main system storage, our internal storage, and SD card storage, which is actually optional for certain devices. Most apps allow you the option to move the app between system and internal storages, but some don't. The ones that can't do that are a bit annoying, especially if they require more space than you'd like them to. As example, some the larger mobile games may require approx half a GB of space, but it has to stay on system storage. I'm not gonna argue with any app devs, but I am generally asking as to why some apps, more specifically, memory expensive ones, don't have that option. We technically need that space for updates and new app installations, and this kind of situation can be really annoying.

 

[Hadron]

We should clarify the language to avoid confusion: you cannot move apps between system storage (/system partition, the ROM) and internal (/data, where user apps, app updates and app data are stored), at least not without root. What is possible on some devices, and for some apps, is to move part of the app between internal (/data) and the removable sd card (not to be confused with /sdcard, which is actually internal). Since 4.0 on most devices /data and /sdcard share the same space, though some older devices and some Chinese ones still use the Gingerbread scheme of keeping these separate.

As for why some apps do not allow it, you'd need an answer from the developer. But possible reasons include performance (may be relevant for games), security (may feel it makes piracy easier), widgets being important to the app, or the app needing to start on boot for other reasons (doesn't work if app moved to sd), or the developer not considering it worth the effort since many devices don't support this anyway.

This problem will be solved in 6.0, which will allow a removable card to be incorporated fully as part of the device storage (at the cost of it behaving like internal storage, so no just popping it into a card reader as it will be encrypted if you choose to do this). It will mean that app's can be fully moved to sd, as opposed to partially or not at all. But only if your device gets the update to Marshmallow.