ClarisWorks / AppleWorks Spreadsheet (.cwk)
The CWK file extension, specifically related to ClarisWorks or AppleWorks Spreadsheets, is a proprietary format used by Apple's productivity suite for spreadsheet data. Originating in the early 1990s, this format allowed users to create and edit spreadsheets on both Mac and Windows platforms. Although AppleWorks was discontinued in 2004 and this format was replaced by NUMBERS, These CWK files can still be opened by older versions of Apple's iWork applications.