The most frequent encounter with an IDX file is in the context of digital movies. In this scenario, the IDX file acts as an index for a corresponding file.
The .idx file extension has its roots in the early days of computing. The term "index" has been used in various forms since the 1960s, primarily in the context of databases and data storage. The .idx file extension emerged as a way to denote index files, which are used to improve data retrieval efficiency in databases, file systems, and other applications. idx file extension