CWK files are associated with ClarisWorks, a office software suite developed by Apple for Mac family of personal computers. CWK files can store text, spreadsheet, presentation, or database documents. ClarisWorks was created as a direct competitor to IBM’s Lotus package and Microsoft Office productivity suite, but didn’t achieve much success.

CWK format is considered obsolete and no modern software supports it. The only way to access data in CWK files is to open the file with a text editor (for example, Microsoft Notepad) and copy the content to a different text file. CWK files saved data in plain text format with additional text markup.