Page Ruler is a Firefox add-on designed for web developers to accurately measure distances on webpages. It enables users to draw a rectangular ruler by simply moving their mouse over the page. The ruler provides real-time metrics, displaying width, height, and the start and end points in pixels, allowing for precise measurements. Activating the add-on is easy; just click the toolbar button, and it can be toggled off with the same action.

In addition to desktop compatibility, Page Ruler is also functional on touch-enabled devices, allowing users to interact with the ruler through touch gestures. This flexibility makes it a versatile tool for various devices. The add-on is subscription-based and focuses on enhancing the web development experience by providing a straightforward way to ensure design accuracy.