Free Ruler is a lightweight on-screen measurement tool for macOS that overlays precise horizontal and vertical rulers directly on your desktop, letting you measure pixels, distances, and layouts without leaving your workflow.
What is Free Ruler?
Free Ruler is a free, open-source macOS utility that places floating ruler overlays on your screen so you can measure any element — a UI component, an image, a gap between buttons — in real time. Developed by Pascal, it runs unobtrusively as a translucent overlay you can drag anywhere on screen, making it an indispensable tool whenever pixel precision matters.
If you've ever eyeballed a margin or squinted at a mockup trying to guess whether that spacing is 12px or 16px, Free Ruler solves that problem in about three seconds. Launch it, drag the rulers into position, and read off the coordinates. That's the entire workflow.
What does Free Ruler do best?
Free Ruler excels at instant, zero-friction on-screen measurement — no screenshots required, no context switching, no paid license needed. The two rulers — one horizontal, one vertical — float independently as semi-transparent overlays, so you can position them around any UI element, design comp, or browser layout and read pixel values directly.
What makes it genuinely useful in daily work is the ruler's origin behavior: you can drag each ruler's zero-point to a specific screen coordinate, then measure relative distances from that anchor. For front-end developers checking that a component lands exactly where a design spec says it should, or for designers eyeballing spacing after a handoff, this single feature saves a surprising amount of back-and-forth with Figma's inspect panel or browser DevTools.
The rulers also respond to your screen's resolution, so on a Retina display you're reading logical points, not raw physical pixels — the number you see is the number that goes in your CSS. I've used this to catch off-by-one padding bugs that DevTools highlighted at zoom level but that I hadn't noticed visually.
Who should use Free Ruler?
Free Ruler is built for anyone whose job involves putting things on screen at specific sizes or positions. That's a wider audience than it sounds: UI/UX designers reviewing implementations against specs, front-end developers debugging layout, technical writers sizing screenshots for documentation, and even presenters making sure slide elements are properly aligned.
If your measurement needs go deeper — think pixel-perfect color sampling, annotated screenshots, or distance measurements baked into exported images — dedicated apps like Sketchbook Measure or xScope 4 offer more horsepower. xScope in particular is the professional's Swiss Army knife of screen measurement, but it costs money and carries real complexity. Free Ruler is the tool you reach for when you need an answer in five seconds and don't want to context-switch out of what you're doing.
Is Free Ruler free?
Yes — Free Ruler is completely free to download and use, with no ads, no in-app purchases, and no subscription. It is distributed as freeware by its developer, Pascal, and is also available via Homebrew Cask (brew install --cask free-ruler) for those who prefer managed installs.
The simplicity of the pricing matches the simplicity of the tool. There's no Pro tier hiding units or ruler accuracy behind a paywall. You get the full utility from the first launch, forever.
How does Free Ruler compare to xScope?
xScope is the professional benchmark — a comprehensive suite of measurement instruments including rulers, guides, crosshairs, a loupe, screen dimensions, and overlay grids, all tightly integrated and backed by active development. It costs around $49 and is worth every cent for designers and developers who live in Figma or Sketch all day. Free Ruler is not a competitor in terms of feature depth; it's a complement or a lightweight alternative for those who only need the ruler function.
The practical calculus is simple: if you need only rulers and you need them now, Free Ruler is the faster answer. If you're doing daily precision work where you also want a loupe, overlay grids, and persistent guide sets, buy xScope. There's also Measure (by Sindre Sorhus) and the built-in screen ruler in Rectangle Pro for those in between.
What are the best Free Ruler alternatives?
For lightweight measurement, ScreenRuler and the ruler built into Rectangle Pro are the closest equivalents. For professional-grade screen measurement, xScope 4 (Iconfactory) remains the gold standard. Rottenwood and Sketchbook Measure cover annotation use-cases that Free Ruler doesn't touch. If you're on a budget and just need ruler overlays, Free Ruler has no real competition at its price point of zero dollars.
