When you enable {% data variables.product.prodname_code_scanning %} on pull requests, the check fails only if one or more alerts of severity error, or security severity critical or high are detected. The check will succeed if alerts with lower severities or security severities are detected. For important codebases, you may want the {% data variables.product.prodname_code_scanning %} check to fail if any alerts are detected, so that the alert must be fixed or dismissed before the code change is merged. For more information about severity levels, see "About alert severity and security severity levels."