About this site
Learn UI is an interactive book about design engineering: the practice of designing interfaces by building them. It is for designers who write code, engineers who care how things feel, and anyone trying to understand why some software seems to respond to intent while most of it merely responds to input.
Eight chapters cover interaction details, motion, components, craft, taste, explanation, canvases, and the career. Each section pairs prose with a figure you operate: you set a spring and watch it ring, swipe a card and see when the action commits, stack toasts and learn why keyframes fail, draw a stroke and change its pressure curve. No interaction shifts the page, and every figure states whether its numbers come from a cited source or are illustrative.
Sources
The book reads the published work of Rauno Freiberg, Emil Kowalski, Maggie Appleton, Bartosz Ciechanowski, Kathryn Gonzalez, Jim Nielsen, Paco Coursey, Steve Ruiz, Amelia Wattenberger, and Andrew Swank, plus the Vercel design engineering team and the hubs that collect the field. None of them are affiliated with this site, and none reviewed it. The chapter prose is original; short quotes are attributed; the glossary quotes its sources verbatim by design; every essay, library, and site cited appears in the reading list with a link.
The rule while writing was simple: no claim without a source, no number a source does not state. When a figure or an explanation gets something wrong, the mistake is this site’s, not the author’s. The originals are better than any summary of them, and the best outcome of reading a section here is that you go and read the essay it draws on.
Who built it
The site does not say, but the Ask AI on any chapter will tell you if you ask.
For developers
Learn UI also publishes a keyless JSON API and an MCP server for the same chapter index. See the developer page.