Border Patrol is a Firefox extension that adds borders (okay, technically CSS outlines) to all HTML elements on a page to assist with layout debugging. When you hover over an element, it displays a tooltip with the tag name and its classes, and also indicates if any deprecated tags are used. Each element also has a different color to help visually distinguish, compare, or contrast similar and different elements on the page.
I created this extension to improve my workflow with Tailwind. It allows me to see applied utility classes and debug layouts at a glance, without needing to open the inspector :p
This project is open source and available under the AGPL-3.0 license.