There are two additional options that are only available if you select the Chrome Crawler - Code Coverage and Accessibility, which you will find in the Advanced Settings.
To get to Advanced Settings, you scroll to the bottom of the main Audit setup page and hit the grey Advanced Settings button.
The Additional Options section is under Crawler -> Additional Options
- Accessibility - Sitebulb will run over 50 automated accessibility checks, across every page on the website. It will highlight accessibility violations and identify opportunities to make your web pages more inclusive and user-friendly.