When using PowerPoint slides in a Canvas course site, two tools can help you quickly check the accessibility of your content: Ally and Microsoft PowerPoint's built-in accessibility checker. 

How to Use Ally to Identify Inaccessible PowerPoint Files

Ally is an accessibility tool that works within Canvas to scan course content and provide feedback to improve accessibility. If your PowerPoint slides are already in Canvas, Ally can be a great way to identify which PowerPoint files need the most attention. 

1. Locate your PowerPoint file in Canvas and look for the gauge icon on the far right.
2. Hover over the gauge icon. You will see an accessibility score. Scores range from low to perfect. The higher the score, the fewer the issues.
   
3. Click the gauge icon to see what needs improvement. Missing image descriptions and insufficient contrast are some common issues Ally can help you address.
   
4. Follow Ally's instructions to fix your file, uploading a replacement by dropping it into the file upload area.

How to Use Microsoft PowerPoint’s Built-In Accessibility Checker

Microsoft PowerPoint's built-in accessibility checker is a powerful tool that can help you identify and address inaccessible content in your slides, especially content not detected by Ally (eg, slide titles, logical reading order).

1. Open your PowerPoint file and then select the Review tab.
2. Click the Check Accessibility button.
   
3. In the Accessibility Assistant pane, you can see all of the issues found by the accessibility checker, including color and contrast, missing alt text, missing or duplicate slide titles, and reading order. From there, you can follow the on-screen tips to address inaccessible content. Don't forget to upload a new copy of your PowerPoint file to your Canvas course site and be sure to delete the older, inaccessible version.
   

NOTE: The instructions featured above were written based on Microsoft PowerPoint for Windows (Version 2412). The interface and features demonstrated may vary based on the version of PowerPoint you use (eg, PowerPoint for web, PowerPoint for macOS). If your version differs from what is depicted, visit the Microsoft Support Center for PowerPoint accessibility tips customized for your version.