Files that contain the .idx file extension are created by a number of DVD playback applications. These files contain information about the subtitles of a DVD, including the subtitle text and start points for when the subtitles should be shown. The IDX file does not contain any actual video data. The video data is contained in an associated video file that is linked to the appropriate IDX file.
The .idx extension is also given to index files. These files contain indexes to database files in order to help speed up the data requests that are sent to a computer database. Some applications that use .idx file extension for index files include Corel WordPerfect, Microsoft Outlook and Quicken.
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