RulerFast
The freeze-frame pixel ruler for Windows. Freeze your screen, drag across anything, and get its exact size in pixels — magnified loupe, automatic edge snapping, and the measurement on your clipboard the moment you let go.
Version 1.0.0 · Single .exe, about 63 MB · No installer, no signup
Freeze. Drag. Done.
RulerFast measures on a frozen photograph of your desktop, so nothing shifts under you mid-drag — and it can never measure its own window by mistake.
1 · Freeze
Press Ctrl+Shift+R from anywhere. RulerFast photographs every monitor at once and shows the frozen frame full-screen — nothing can shift under you mid-measurement.
2 · Drag
Drag across anything — a button, a margin, an image, a gap. A magnified loupe follows the cursor and edge snapping locks your endpoints onto real edges, no pixel-hunting.
3 · Done
Release, and the exact size in pixels is already on your clipboard — “240 × 64 px” goes straight into a spec. The region is kept in your library automatically.
Built for pixel-perfect work
Everything is tuned for one job: landing on the exact pixel, first time, and getting the number where you need it with zero friction.
Magnified loupe
A large, smooth magnifier glides with the cursor and shows the exact pixel your endpoint will use. Roll the mouse wheel to zoom further in.
Edge snapping
RulerFast finds the strong colour change near your cursor and snaps to it — separately per axis — so you lock onto the true edge of a button or box.
Real physical pixels
Measurements are in the screen’s true device pixels, even on a 150%-scaled display — exactly what you want when checking a layout or a CSS value.
Auto-copy on release
The moment you let go, “W × H px” is on your clipboard. No extra click between measuring and pasting into a spec, ticket or stylesheet.
Screenshot library
Every kept region lands in a persistent library with folders, drag-to-reorder, renaming, previews and rounded-corner exports to PNG, JPEG, BMP, GIF or TIFF.
Portable datasets
Save your entire library — index and images — into a single .rfdataset file you can archive or move to another PC, and merge back in without overwriting anything.
Fully offline
No internet needed, ever. No account, no telemetry, nothing leaves your machine. One standalone .exe with the RulerFast logo on your taskbar.
Light & dark themes
Flip the whole interface between the dark FastSites theme and a clean light theme. Your choice — like your loupe zoom and save folder — is remembered.
Fast under your fingers
Every action has a key, and a Shortcuts menu in the app lists them all.
- Freeze the screen from anywhereCtrlShiftR
- Constrain to a straight horizontal / vertical lineShift
- Perfect square while drawing or resizingCtrl
- Ignore edge snapping for a freehand endpointAlt
- Confirm — keeps the region in your libraryEnter
- Keep the region and stay to capture moreK
- Save the region or screen to a fileS
- Copy the measurement againC
When you’ll reach for it
- Check a built page against its design spec without leaving the browser
- Grab the exact dimensions of a button, margin or gap for a CSS value
- Measure images and media before exporting or cropping
- Audit spacing consistency across a whole screen, even spanning monitors
- Capture pixel-exact regions into an organised, permanent screenshot library
Built with integrity
Open source, fully offline, and defensive by design — RulerFast even verifies every screen capture and automatically retries if Windows hands it a blank frame, so your first capture is never a black one.
Questions, answered
Is RulerFast free?
Yes — completely free. No signup, no license key, no trial period. It is part of the FastSites toolkit.
Does it need an internet connection?
No. RulerFast is fully offline — it never phones home, and your screenshots never leave your machine. They are stored locally in %AppData%\RulerFast.
Which platforms does it support?
Windows 10 and Windows 11. There is no macOS or Linux version.
Do I need to install anything?
No installer and no runtime to set up — RulerFast ships as a single self-contained .exe. Download it, double-click it, and it runs. Copy the file anywhere you like.
Windows showed a SmartScreen warning — is that normal?
Yes. New downloads that are not code-signed commonly trigger SmartScreen. Click “More info”, then “Run anyway”. RulerFast is open source, so you can also audit the code and build the exe yourself with one double-click of build.bat.
Are the measurements affected by Windows display scaling?
No — that is the point. RulerFast measures in the screen’s true physical pixels, so on a 125% or 150% scaled display you still get the real device-pixel size.
Measure it exactly, from the next click
One download, no installer, no account. RulerFast is part of the FastSites toolkit — built to sit beside the editor and the rest of your workflow.
Explore the rest of the toolkit at fastsites.app/toolkit