MicroSD memory cards are memory card expansions for small electronic devices, most often telephones. They also get used in smaller cameras, digital recorders and similar electronic devices. Not all phones have them; for example, Apple's iPhone does not have a MicroSD card, though most Android phones and tablets do. Moving data to and from the MicroSD card is much like moving files around from your laptop computer to a thumb drive or other removable media.
Devices That Use the MicroSD Card
To get the most out of your MicroSD card you may need to have root access to your phone, or the ability to browse through folders on the phone like you would on a computer desktop. For Android phones, this ability may already be present, and different manufacturers allow different levels of access to the directory structure. If your phone doesn't allow this, look for a program called "CyanogenMod" and read up on how to use it to get full access to your phone's directory structure (and other features). Note that rooting your phone may void your warranty. Even without full root access to your phone, several things can be done to make use of the MicroSD card. Setting up your microSD card as the default save location for your phone's camera is one; several phones from HTC and Samsung ask if you want to do this when the card is inserted. Google has made this one of the default behaviors in Android 4.0 and later, though not all phones have gotten this update. The MicroSD card can store any kind of file your phone can use, so it's also good for music and ringtone files.
Accessing MicroSD Storage
When you insert a MicroSD card in the phone, the operating system mounts it as an external memory source. On Android phones your MicroSD card shows up as "SD Card Storage," alongside "Device Memory" and "USB" storage separately. "Device Memory" is memory that's specifically reserved for the operating system. "USB" is whatever inherent storage the phone has, and "SD Card Storage" is the detected capacity of your MicroSD card.
Applications and the MicroSD Card
You can put a MicroSD card in their phone to store data from applications. If you can see the folder where your application stores data, you can move it to the MicroSD card. Applications that require the user to pay for them and applications or programs that are part of the phone's operating system can't be put into a MicroSD card, but most everything else can -- although sometimes it takes experimentation to figure out just how. Paid applications have this restriction to prevent unauthorized sharing.
MicroSD Cards and SD Card Readers
MicroSD cards come with adapter plates. These are SD-sized cards that you can slide the MicroSD card into, and then slip into a standard SD card-reader slot. These adapters make it possible to use MicroSD cards for moving data between a telephone and computer without having a Wi-Fi or cable connection. This ability is particularly useful when moving large multimedia files between the two devices, like movies or photo libraries.
Kinds of MicroSD Cards
While MicroSD card capacities range from 2GB to 128GB, not all cellular phones can read or write to the larger capacity cards. Before buying the largest card available, check your telephone's hardware specifications. For example, they may specify that it reads SDHC MicroSD cards, which have a maximum capacity of 32GB. If it says "Standard SD," it's limited to 2GB of storage. Newer phones may implement some variety of SDXC, which will let them mount a 64GB or 128GB card. Check to see if the hardware manufacturer specifies a specific maximum card size that's lower than the defined standard.
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