A bookmarklet is a small JavaScript program stored as a URL within a web browser's bookmarks. When clicked, it performs a specific function on the current webpage, such as changing the page's appearance, extracting information, or automating tasks. Bookmarklets are easy to create and can enhance browsing efficiency without needing to install additional software. These handy tools work across different web browsers, including Google Chrome, Mozilla Firefox, and Safari. Users can save bookmarklets just like regular bookmarks, making them accessible with a single click. They are particularly useful for web developers and power users looking to streamline their online activities.