Follow these steps to delete the custom domain of your Looker (Google Cloud core) instance:
- On the Instances page, click the name of the instance for which you would like to remove the custom domain.
- Select the CUSTOM DOMAIN tab.
- Select the Delete trash icon next in the domain mapping.
- In the deletion dialog, type "delete" into the text field and select CONFIRM.
Once the domain mapping is deleted, you will be directed to the Instances page in the Google Cloud console. The Instance URL on the page will revert the default domain that was assigned when the Looker (Google Cloud core) instance was created.