The extension .ZIM refers to files of the type OpenZim wiki archive files. This is one of the popular formats for storing wikis. The file archive was developed as a part of the OpenZim project.

The file structure of a wiki article or a wiki file collection is defined in a well-organized manner and there are some predefined rules for storing the questions and answers in a particular format. The .ZIM wiki files are useful in organizing articles, references and other general information in a crisp and compact way. The ZIM wiki archive files are supported by many third party readers like ZIMreader and kiwix.