Adobe Captivate creates a backup file for your project when you save it. When you re-save the project, the changes are saved to the backup file too. The backup file is saved with a .bak extension.
If your project file gets corrupt, use the backup file to recover your project. Rename the backup file using a .cptx extension, and open it. Changes that you made after the last save, however, are not reflected in the backup file.
The provision to create a backup file is enabled by default in the Preferences dialog box. You can choose to disable the option if it interferes with the speed of saving the project.
The size of the backup file might be larger than that of your main project.