Peacekeeper is a free add-on for the Chrome browser that provides website notifications. Developed by Yuki Adachi, this add-on allows users to receive notifications for each website they specify.

With Peacekeeper, users can easily determine the server environment they are accessing, whether it is local, development, test, staging, or production. The add-on offers various notification methods to alert users, including pop-up alerts, changes to the website's favicon, and changes to the website's style.

This add-on is a valuable tool for web developers and testers who need to keep track of the server environment they are working with. Peacekeeper helps ensure that users are always aware of the website they are accessing and can easily distinguish between different server environments.