Android 6.0 Marshmallow has a new feature that can turn your external micro SD card into internal memory.
When the SD card is inserted and recognized, Android will give you an option of using the SD card as internal memory or as a location for files. Let’s break it down…
- Internal memory – If you are running an old phone with little internal memory, you can choose this option. You will sacrifice speed for storage.
- Transferring files – If your phone already has a good amount of internal memory, then select this option. Your apps will be able to use the external SD card as before for saving large offline content, saving your internal memory for apps and speed.
If you are not sure what you selected, apps will not recognized any external SD card if you are using it as internal memory.
If you are trying to undo selecting the internal memory option by using your laptop, you will be met with limited success. Android has to do some funky partitioning of the SD card because on my 32gb and 64gb micro SD cards, my Windows and Linux laptops could only see a 17mb partition. To fix that, insert your micro SD card into another Android phone and do a format with that phone. It can see the funky partitions and recover your micro SD card.
If you are using CyanogenMod 13 to run your phone, as of the writing of this article, the OS was very bugging when using the internal memory option with apps crashing constantly.
Sources:
Man and Keyboard 