Metis от FrodoWho

A lightweight design tool right in your browser for inspecting element dimensions and dropping alignment guides on any web page.

There are two main features:

• Measure mode
You can just hover over an element to check its width, height, padding, margin, and position. If you want to keep those numbers on screen, click to lock them in place. You can lock down as many elements as you need.

• Guides mode
You can click to drop vertical or horizontal guide lines. They'll automatically snap to the edges and centers of elements, but you can hold down Shift to bypass the snapping. You can also turn on gap labels to easily see the distance between your guides.

Helpful shortcuts:
• Press Alt+Shift+M (⌥⇧M on Mac) to toggle the toolbar.
• Press V or H to quickly switch your guide direction.

It's completely private. There's no tracking, no analytics, and no account required. Just open it up and start measuring.