Software & Apps File Types What Is an IDX File? How to open, edit, and convert IDX files By Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated December 16, 2019 File Types Design Cryptocurrency MS Office Windows Linux Google Drive Apps File Types Backup & Utilities View More Tweet Share Email A file with the .IDX file extension might be a movie subtitle file used with videos to hold the text that should be displayed in the subtitles. They're similar to other subtitle formats like SRT and SUB, and are sometimes referred to as VobSub files. IDX files are also used for Navigation POI files, but they have nothing to do with the subtitle format. Instead, VDO Dayton GPS devices store points of interest in the file that the device can refer to during a trip. IDX is also an acronym for Internet Data Exchange and Information Data Exchange, but neither have anything to do with computer file formats. Other IDX Files Some IDX files are just general index files that a program creates to refer to for speedier functions, like to search through a large number of files. One specific use is as HMI Historical Log Index files that some applications use to run reports. Another similar index-related file format that uses the IDX file extension is Outlook Express Mailbox Index. The MS Outlook Express program stores an index of messages taken from an MBX file (Outlook Express Mailbox). The IDX file is required in order to import older mailboxes into Outlook Express 5 and newer. How to Open IDX Files If you know that your file is in the Movie Subtitle format, you should first decide what you want to do with it. To display the subtitles along with a video requires that you open the IDX file in a video playback program like VLC, GOM Player, PotPlayer, or PowerDVD. Otherwise, you can edit the IDX file to change the subtitles with a tool like DVDSubEdit or Subtitle Workshop. You can use VLC to see the subtitles with your video on macOS and Linux, but MPlayer for Mac and SMPlayer for Linux work, too. The video player might need to have the movie open and ready to play before it will let you import the Movie Subtitle file. This is true for VLC and probably similar media players. Navigation POI files are not used on a computer but instead just transferred to the VDO Dayton GPS device over USB. However, you might be able to open them with a text editor like Notepad++ to see the coordinates, POI name, and type, etc. A few examples of programs that use index files include ICQ and ArcGIS Pro. Wonderware InTouch opens IDX files that are HMI Historical Log Index files. Microsoft Outlook Express utilizes the IDX file in that format. IDX0 files are related to IDX files in that they're Runescape Cache Index files. Like the other index files mentioned here, IDX0 files are used by a specific program (RuneScape) to hold cached files. They're not meant to be opened manually. How to Convert an IDX File Because there are a few different file formats that use the IDX file extension, it's important to recognize which format your file is in before you decide which program is needed to convert it. Movie Subtitle files normally come with a DVD or video download. If that's the case, you can convert the IDX file to SRT with a tool like Subtitle Edit. You might also have luck using an online subtitle converter like the one from Rest7.com or GoTranscript.com. Please know that you can't convert an IDX file to AVI, MP3, or any other media file format. This is because the IDX file is a text-based, subtitle format that doesn't contain any video or audio data. It might seem like it does since the file is usually used along with videos, but the two are very different. Actual video content (the AVI, MP4, etc.) can only be converted to other video file formats with a video file converter, and the subtitle file can only be saved to other text formats. It's unlikely that a Navigation POI file can be converted to any other format. That type of IDX file is probably only used with the VDO Dayton GPS device. It's hard to know for sure whether your index file can be converted to a new format but chances are it can not, or at least shouldn't be. Since index files are used by specific programs for data recall, they should remain in the format that they were created in. For example, if you managed to convert an Outlook Express Mailbox Index file to CSV or some other text-based format, the program that needs it won't be able to use it. The same concept can be applied to any other file format that uses the IDX file extension. However, since some index files might just be plain text files, you might be able to convert the IDX file to TXT or an Excel-based format to view it as an Excel spreadsheet. Again, this would break the functionality of the file but it would let you see the text contents. You can try this by opening the file in Excel or Notepad and then saving it to any of the supported output formats.