1. Navigate to the Grades page and click the Actions menu.

  2. Click Export Entire Gradebook. If you wish to choose only specific gradebook item, filter the necessary gradebook items, and click Export Current Gradebook View.

  3. When the export is completed, Canvas downloads the CSV file automatically to your computer.

For more details, see How do I export grades in the Gradebook? - Instructure Community (canvaslms.com)