What Is an IDX File?

One kind of IDX file is for movie subtitles, but there are several other formats that use this file extension

What to Know

  • Some IDX files are movie subtitles. VLC, GOM Player, and PotPlayer are a few media players that support that format.
  • You can convert the subtitles to an SRT file with Subtitle Edit.
  • Other IDX files are different. For example, VDO Dayton GPS devices use IDX files for points of interest.

This article explains what an IDX file is, how to open one, and how to convert one to a different file format.

What Is an IDX File?

A file with the .IDX file extension might be a movie subtitle file used to display subtitle text on videos. Sometimes referred to as a VobSub file, it's always accompanied by a SUB file (which contains the actual images that include the subtitle text)—it describes where and when to show the images.

Other IDX files are used for navigation points of interest, 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 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 this extension is Outlook Express Mailbox Index. The 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.

IDX is also short for Internet Data Exchange and Information Data Exchange, but neither have anything to do with computer file formats.

How to Open IDX Files

If you know that your file is in the 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.

For example, to see the subtitles in VLC, go to Subtitle > Add Subtitle File to find and select the file.

IDX subtitle selected in VLC
VLC importing an IDX file.

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 subtitles. This is true for VLC and probably similar media players.

Navigation POI files aren't 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. AVEVA's InTouch HMI opens IDX files that are log index files. 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 different formats that use this file extension, it's important to recognize which format your file is in before you decide which program is needed to convert it.

Movie subtitles 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 converter like the one at GoTranscript.

You can't convert an IDX file to AVI, MP3, or any other media file format. This is because the file is text-based and 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 certain GPS devices.

It's hard to know for sure whether your index file can be converted to a new format, but chances are it can't, 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 a similar 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 a 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.

Still Can't Open It?

Lots of file extensions use the same letters, some with just a few rearranged in a different order. But two extensions that look similar don't necessarily have anything in common, meaning that they don't always open with the same software.

If your file isn't opening with the suggestions above, there's a really good chance you're simply misreading the file extension.

IDW files, for example, look a lot like the file extension talked about on this page, but they're actually vector-based drawings created by Autodesk Inventor. You need that software to open that particular file type, so trying to plug it into the programs linked above won't get you far.

Some, however, are in fact a little similar but still don't open in the same way as described above. An IX file is one example. It's an index file, too, but is created and used by dtSearch.

Several other examples could be given, like ID, IDB, and IDV. Be sure you're reading the file extension correctly. If you have a different file than what this article covers, try searching for it here on Lifewire or Google to learn more about the format and find the programs that are able to open or convert it.

  • Is it safe to delete IDX files?

    Yes. Deleting IDX files included with video files will not render the video unplayable. Of course, you won't have subtitles.

  • What are IDX files used for in databases?

    In database management systems, IDX stands for index. IDX files represent tables sorted by key values, which are used to retrieve data as quickly as possible. Database systems that use IDX files include Advantage, DBISAM, Foxpro/DBase, and Informix.

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