What are IDX files?

This article explains what an IDX file is, how to open it, and how to convert it to another file format.

What are IDX files?

A file with the .IDX file extension can be a movie subtitle file used to display subtitle text on a video. Sometimes called a VobSub file, it is always accompanied by a SUB file (containing the actual images including subtitle text) - it describes where and when the image is displayed.

Other IDX files are used for navigational points of interest, but they have nothing to do with the subtitle format. Instead, the VDO Dayton GPS device stores points of interest to a file that the device can refer to along the way.

Some IDX files are just general index files that the program creates for reference for faster functions, such as searching through a large number of files. One specific use is the HMI history log index file 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 MBX (Outlook Express Mailbox) files. An IDX file is required to import older mailboxes into Outlook Express 5 or later.

Note : IDX also stands for Internet Data Exchange and Information Data Exchange, but has nothing to do with computer file formats.

How to open IDX files

If you know that your file is in subtitle format, you should first decide what you want to do with it.

To display subtitles with the video, you must open the IDX file in a video player such as VLC Media Player, GOM Player, PotPlayer or PowerDVD. If not, you can edit the IDX file to change the subtitles using a tool like DVDSubEdit or Subtitle Workshop.

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

You can use VLC to watch video subtitles on macOS and Linux, and MPlayer for Mac and SMPlayer for Linux work just as well.

Tip : The video player may need to have the movie open and ready to play before allowing you to enter subtitles. This is true of VLC and probably similar media players.

Navigation POI files are not used on the computer but instead are only transferred to the VDO Dayton GPS device via USB. However, you can open them with a text editor like Notepad++ to see the coordinates, POI name and type, etc.

Some examples of programs that use index files include ICQ and ArcGIS Pro. AVEVA's InTouch HMI opens IDX files as journal index files. Outlook Express uses IDX files in that format.

IDX0 files are related to IDX files in that they are Runescape cache index files. Like the other index files mentioned here, IDX0 files are used by a specific program, RuneScape, to store cached files. They are not meant to be opened manually.

How to convert IDX files

Since there are many different formats that use this file extension, it is important to identify which format your file is in before deciding which program is needed to convert the file.

Movie subtitles often come with DVD or video downloads. If that's the case, you can convert the IDX file to SRT using a tool like Subtitle Edit. You may also have luck using an online converter like the one at GoTranscript.

Note : You cannot convert IDX files to AVI, MP3 or any other media file format. This is because the file is text-based and does not contain any video or audio data. It may seem so because the file is often used in conjunction with video, but the two files are very different. Actual video content (AVI, MP4, etc.) can only be converted to other video file formats using a video file converter, and subtitle files can only be saved to other text formats.

Navigation POI files can hardly be converted to any other format. That type of IDX file may only be used with certain GPS devices.

It's hard to know for sure whether your index file can be converted to the new format, but chances are it can't, or at least it shouldn't. Because index files are used by specific programs to retrieve data, they must retain the format in which they were created.

For example, if you need to convert an Outlook Express Mailbox Index file to CSV or a similar format, the program that needs that file will not be able to use it. The same concept can be applied to any other file format that uses the IDX file extension.

However, because some index files may just be plain text files, you can convert the IDX file to a TXT or Excel-based format to view the file as a spreadsheet. Again, this will break the functionality of the file but it will allow you to view the text content. You can try this by opening the file in Excel or Notepad and then saving it to any of the supported output formats.