Magento 2 Developer Toolbar is the Magento 2 equivalent of https://github.com/balloz/magento-developer-toolbar.
The toolbar provides the Magento developer with four debug panels:
- Info - Shows various bits of information about your installation and the current request
- Layout - The Magento 2 layout used to render the current page, allowing you to view the containers, blocks and templates used
- Handles - All layout handles that applied to the current page
- Queries - All database queries performed to render the current page