Grids & Ruler is a Firefox extension designed for web developers, providing a dedicated panel within the Firefox developer tools. This tool allows users to create and manage overlays on web pages, offering visual guidance that aids in developing precise layouts for web applications. The extension is particularly useful for ensuring consistent spacing and alignment, which are critical for responsive design.

The interface is user-friendly, allowing developers to customize grids and rulers according to their project requirements. With its subscription-based model, Grids & Ruler aims to streamline the web development process, making it easier for developers to visualize their designs and enhance the overall quality of their web applications.