One of the most beautiful feature on Android 6.0 Marshmallow is that you can use the external SD card as internal storage on your device. Meaning the system will secure and adopt the SD card as its own and hence lift all restrictions as to access from apps, and most importantly, it’ll completely shift the app storage burden on internal storage to the SD card.

This also makes your SD card secure and ties it to your device only. Once you format your external SD card as internal storage on Marshmallow, it can only be used on the same device then. To use it on other devices, a format will be required, which ensures the safety of your data on the SD card.

And for super budget devices like Android One phones, which come with internal storage as low as 4GB, it solves the low storage issue as it allows the system to install apps on SD card directly (once adopted as internal) with complete data and obb files.

Of course, this feature has no use for devices with no SD card support (like Nexuses, Galaxy S6, Note 5, Moto X, etc.), but Android One and many other devices with SD card support will find this very useful to secure their SD card data and extend internal storage capacity.

How to turn external SD card into internal storage on Marshmallow
  1. Go to device “Settings” > select “Storage”.
  2. Select your SD Card > tap the three-dot menu on top-right corner > and select “Settings” from there.
  3. Select “Format as internal” > and then “Erase & Format” on the next screen.
  4. Your SD Card will now be formatted as internal storage.
  5. Reboot phone.
    └ This is very important, otherwise you may end up frustrated with issues like MTP not showing SD card, some apps not working properly, etc.

That’s all. Enjoy your extended internal storage and freedom from low storage space issue.

Happy Androiding!