SD cards are used to provide expandable storage to a huge range of devices form cell phones and cameras, to gaming systems and laptop computers. Every SD card that is made must have a CID in order to interface with another device. The CID is a special identifying code that is unique to each card, working in the same fashion as a serial number. The CID is not usually displayed anywhere on the device, and few manufacturers provide a way of retrieving this information. With the help of a free, open source application, you'll be able to read the CID of any SD card in less than five minutes.
Navigate to the ReadCID download page (see Resources).
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Download the ReadCID software, and install it to your local hard drive.
Insert the SD card you wish to use into your computer's SD card slot.
Run the ReadCID software. Click on the drop-down menu at the top of the program window to select your SD card from the list of available drives. The software should load for a few seconds then provide the SD card's CID in the "Product Serial Number" field.