The project’s own promotional image. The repo’s notice states it is a stylised mockup rather than a screenshot; the reference plates in docs/collection/ are the real renderer.
A menu-bar app that wraps every window in a knitted border — Finder in blue checks, Claude in cream stars on apricot wool, Notion in ivory and charcoal — so you can tell one window from another without reading a single title bar.
“Felt chilly today so knitted little sweaters for my windows,” Sara Gordic posted on 12 September, with an eighteen-second video attached. The repo went public three days later and had 578 stars by the weekend. Grant it Accessibility access so it can follow which window has focus, and it draws a border of rendered knitwear around each one.
The collection is the part that took the work: 37 hand-picked colourways, one per app. Mail gets envelope scallops, Zoom gets linked little windows, Photos gets rainbow posies across six petal colours. Spotify and Notion both get raised checks, in leaf-green-and-butter and in ivory-and-charcoal. Notes and Calendar break the pattern with a continuous curved cuff on the outer edge instead of a patterned corner; WhatsApp gets textured corner patches. Codex and ChatGPT deliberately share one colourway. Anything with no design of its own falls back to a two-colour zigzag, picnic or twinkle, knitted in shades lifted from its own icon.
The repo is straight about what it stands on. Window Sweaters is derived from Felix Kratz’s JankyBorders and ships a notice saying so; what Gordic added is the procedural knit renderer, the colourways, the menu-bar controls and the window tracking. It is GPL-3.0, written in C and Objective-C, and it reaches the window server through private macOS APIs — which the README states plainly, along with the consequence that a system update can change how it behaves.
The other rough edges are documented rather than buried. Borders vanish while you drag a window’s edge and return when you let go. Version 1.4.28 was compiled against macOS 26 by mistake and refused to launch on anything older despite declaring macOS 13 as its minimum, fixed the next day in 1.4.29; 1.4.30 and earlier shared a Mach service name with JankyBorders, so having both installed stopped this one starting, fixed in 1.4.31. It is not notarised, so the first launch needs a detour through Privacy & Security. Install by Homebrew cask, or unzip the build from Releases. The author has only tested it hands-on on Apple Silicon running macOS 26.
The case for keeping it is not the knitting. A window edge is the one piece of chrome your eye crosses hundreds of times an hour and the one thing every Mac app renders identically — and a green-and-cream picnic check is findable across a crowded desktop in a way that four words of title bar are not.