Caliper

Grid, guide lines & measurement tools for any webpage

Caliper is a layout inspection extension for designers and frontend developers. It adds a lightweight overlay on top of any webpage so you can check grids, spacing, guides, rulers, breakpoints, and element measurements without leaving the page. Use Caliper to toggle a column grid, baseline grid, draggable guides, pixel rulers, cursor coordinates, and measurement mode. It also shows viewport size, DPR, and responsive breakpoint information to help you validate layout behavior quickly. Guides and preferences are saved per site, so you can return to a page and keep working with the same setup. Keyboard shortcuts make it easy to switch between grid, guides, and measurement tools while reviewing real pages in context.