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Index file
File type: System file, Database file
Files with idx extension can be usually encountered as various index files from all kind of programs and applications.
Found 7 different file type records with the same idx filename suffix.
File type category:
System file
Database file
Date updated: November 25, 2022
File extension idx is traditionally used for index files. Many programs use them, but no unified format exists. Nevertheless, they are generated for the very same purposes - to speed up file or database search. You may find these indexes mainly in database programs, but even some video subtitling programs or media players use them.
These files are usually generated by programs to speed up the searching through large number of files. In most cases if you delete this file, it will be recreated the next time the index process is started again.
Index files usually contain one header record and one or many node records. The header record contains information about the root node, the current file size, the length of the key, index options and signature, and printable ASCII representations of the key1 and FOR expressions. The header record starts at file position zero.
Note: There is no connection to Internet Data Exchange and this file type.
Most of index files are not meant to be opened directly and only serve for indexing purposes. Some may be opened using a text editor, but lots of them are binary.
Index files are typically not meant to be converted to anything else.
Software apps that create idx files:
Microsoft Windows
Multiplatform
Software applications that handle other tasks involving idx files:
Microsoft Windows
Multiplatform
File type category:
Text file
Date updated: June 19, 2018
The idx file extension is also used in Easy Timesheets, a program for one of its data format. Easy Timesheets is a multi-user timesheet and time recording software.
The idx file stores data.
Can be opened by text editor (Notepad, Notepad++).
Probably cannot be converted to other formats.
Software applications that handle other tasks involving idx files:
Microsoft Windows
Easy Timesheets
File type category:
Game file
Date updated: June 22, 2019
Record marked as obsolete and not updated for a long time.
The idx file extension is associated with the computer game Hellgate: London. The idx file contains game data.
Most likely some old format without support. No further information could be found.
Software applications that handle other tasks involving idx files:
Microsoft Windows
File type category:
Various data file
Date updated: June 18, 2018
Record marked as obsolete and not updated for a long time.
The idx file extension is associated with Microsoft Outlook Express, an e-mail and news client included in earlier releases of Microsoft Internet Explorer.
The latest edition of Outlook Express is called Microsoft Mail Live.
The idx files are used for indexing of mail messages.
Use Microsoft Outlook Express.
Software apps that create idx files:
Microsoft Windows
Software apps that recover idx files:
Microsoft Windows
Software applications that handle other tasks involving idx files:
Microsoft Windows
File type category:
Game file
Date updated: December 13, 2018
Record marked as obsolete and not updated for a long time.
The idx file extension is associated with NoX, an action role-playing game developed by Westwood Studios and released in 2000.
The idx file contains various data resources for NoX game.
Probably not meant to be accessed by the user.
Probably cannot be converted to anything else.
Software applications that handle other tasks involving idx files:
Microsoft Windows
File type category:
Various data file
Date updated: July 13, 2025
File extension idx is also used for subtitle index files. These are typically found along actual (graphics) movie subtitles (.sub etc.) and act as metadata and index files. Usually contain timing, language, and bitmap information (colors) but not the subtitles.
Both the index and the associated subtitle file is needed for a successful playback of graphic SUB subtitles. Text based subtitles do not need these files at all.
Some media players, such as VLC player allow importing of these .idx files. However, this will only work if you have the actual subtitles (usually .sub) that are linked in the .idx file.
You most likely cannot convert the indexes alone. You will also need the actual subtitles and convert both files together.
Software applications that can open idx files:
Microsoft Windows
Software applications that can edit idx files:
Microsoft Windows
Software capable of saving idx files:
Microsoft Windows
Software apps that import idx files:
Microsoft Windows
Apple macOS / Mac OS X
Linux/Unix
Apple iOS
Google Android
File type category:
Various data file
Date updated: April 23, 2019
Record marked as obsolete and not updated for a long time.
The idx file extension used by Sunnysoft InterWrite, a software for Windows Mobile platform.
The idx file contains some kind of data used by InterWrite.
Most likely some old format without support. No further information could be found.
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