.CWK File Extension

Document created by Apple's AppleWorks or ClarisWorks productivity suite; can be a word processing document, spreadsheet, or presentation; can still be opened by iWork applications (Pages, Numbers, Keynote), but the file must first be in the AppleWorks 6 format and importing results may vary.

Apple acquired ClarisWorks in 1998 and renamed it to AppleWorks. Both productivity suites were available in Mac and Windows versions. However, AppleWorks has been discontinued and was last updated in 2004.