A tiny macOS menu-bar app that draws a colored outline around every window, with one stable color per app — so when you have a dozen windows open you can tell at a glance which is which.
It reads only each window's position and owning app, so it needs no screen recording permission. The outlines are transparent and click-through, and each one is layered just above its own window, so they don't get in your way.
make appRequires the Xcode Command Line Tools (clang). macOS 13+.
make installThis builds the app and copies it to /Applications. Open it once, then click
the ⬜ menu-bar icon and choose Open at Login so it starts automatically with
every login — no Terminal needed after that.
open WindowBorder.appIf you got a prebuilt copy instead of building it yourself, it's unsigned, so macOS Gatekeeper may refuse to open it on first launch. Either right-click the app and choose Open, or clear the quarantine flag:
xattr -dr com.apple.quarantine WindowBorder.app. Building from source (above) avoids this entirely.
It lives in the menu bar (look for the ⬜ icon). Open windows get an outline; the color is assigned per app and stays consistent. Move or resize a window and its outline follows.
From the menu bar icon:
- Borders On/Off — toggle the outlines
- Reload Colors — re-read your color config
- Open at Login — start automatically when you log in
- Quit
By default each app gets the next color from a built-in palette. To pin specific
apps to specific colors, create ~/.config/window-border/colors.json:
{
"Safari": "#1E90FF",
"Finder": "#FF3B30",
"Terminal": "#34C759",
"Code": "#AF52DE",
"Google Chrome": "#FFCC00"
}Keys are the app names as macOS reports them; values are hex colors. Then pick Reload Colors from the menu. Apps not listed keep getting palette colors.
CGWindowListgives the on-screen windows, their bounds, and owning app.- For each window we keep a transparent, click-through overlay window the same size, drawing a rounded-rect stroke in the app's color.
- Each overlay is ordered just above its target window, so the borders layer the same way your windows do.
- A light timer (~20 Hz) keeps the outlines following moves and resizes.
- The outline tracks via polling, so during a fast drag it can lag a frame.
- Multi-display setups use the primary display as the coordinate reference; edge cases on mixed-resolution layouts are possible.
- It draws around normal app windows only (not menus, panels, or the desktop).
MIT