Window Sweaters

Window Sweaters is an open-source macOS menu-bar utility that adds knitted-looking borders to application windows, turning window management into a desktop customization feature. Users can adjust the border style, pattern, width, and stitch size from a yarn icon in the menu bar, pause the effect, or disable it for individual apps. A “By App” mode gives applications distinct designs, while “Zigzag” applies a coordinated cream zigzag using colors drawn from app icons. The project includes hand-designed colorways for 37 apps, spanning Apple software, productivity tools, coding assistants, design programs, and browsers; other apps can receive generated yarn colors. Users can also define custom colors and patterns.

The app requires macOS 13 or later and Accessibility permission to track the focused window. It is available through Homebrew, a downloadable release, or a build-from-source process using Apple’s Command Line Tools and Python. Its creator describes it as a personal project with rough edges: borders disappear during window resizing, and the app relies on private macOS window APIs that may be affected by system updates. Testing has primarily been on Apple Silicon with macOS 26, so support on older systems and Intel Macs is less established. The code is licensed under GPL-3.0 and builds on JankyBorders, with instructions for reporting issues, contributing tests, and creating custom sweater charts.