You can figure out what your Kindle's generation is by deciphering it's physical characteristics. Knowing what generation of Kindle you have is helpful because you will know what features are available on the device. Although the main feature of a Kindle is to download e-books for immediate reading, one version of a Kindle may have a feature another will not. For example, the third generation of the Kindle has a built-in wireless adapter and can access Wi-Fi networks.
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Turn your Kindle over and look in the back for an SD card slot. If you find one, you have the original Kindle or first generation. The first generation Kindle is the only one with an SD card slot.
Observe the location of the five-way controller. If it is to the right of the keyboard, it is the second generation Kindle.
Measure the size of the screen. If the screen size is 9.7 inches, it is the DX version of the Kindle.
Inspect the keyboard on your Kindle. If the five-way controller is located in the keyboard along with the other keys, it is the third generation Kindle.