Devicon

Shows when you are on a dev-version of a page by putting a border around the favicon.

Looks at the URL of the page you're on to see if it's a dev environment and adds a border to the favicon so you can easily tell if you're on a dev environment or not. You can change in the options what URL hostname constitutes a dev environment, by default we look for: - localhost - 127.0.0.1 - Sites ending with .test