An SDX file is a file used by Kivuto Solutions' Secure Download Manager (SDM), a program used for downloading files from web stores such as DreamSpark and OnTheHub. It saves information required to download the purchased item, but does not contain the actual purchased item itself.

An SDX file is downloaded from the web store when you purchase an item and click to download it. When the file is opened, SDM begins the download process for the purchased item. Secure Download Manager integrates with web browsers on both Mac and Windows platforms. Depending on the browser you're using, SDM may or may not automatically open an SDX file after it's been downloaded. Therefore, you may need to remember the download location for your SDX file and then open it manually to download your purchase.