The ShareX ruler is a full-desktop pixel measurement overlay. It can measure the length of a same-color run under the pointer or the width and height of a selected rectangular area. It is useful for checking UI spacing, element sizes, margins, borders and alignment directly on screen.
Open it from Tools -> Ruler.
The ruler captures the desktop when it opens. If the underlying screen content changes, close and reopen the ruler to measure the updated pixels.
Press H for horizontal measurement, V for vertical measurement, or Space to switch between them. A middle-click also toggles the axis at the pointer.
Use the mouse wheel to change color tolerance. A low tolerance stops at small color differences; a higher tolerance can treat anti-aliased edges or gradients as part of the same visual run. The current tolerance percentage appears temporarily on screen.
| Keybind | Action |
|---|---|
| H | Use horizontal measurement |
| V | Use vertical measurement |
| Space or middle-click | Toggle measurement axis |
| Arrow keys | Move the most recent measurement by 1 pixel |
| Shift + arrow keys | Move the most recent measurement by 10 pixels |
| Ctrl + C | Copy the most recent measurement text |
| Delete | Clear all measurements |
| Esc | Close the ruler |
For the most reliable result, zoom the application to 100% and account for Windows display scaling when comparing on-screen pixels with CSS or design-tool dimensions.