The chassis of a tool application, in 8 kB
panels
panels is a React library by Alban Pasquelin providing the chassis of a tool application (icon rails, resizable zones, a free centre with draggable tabs) in 8 kB gzipped, with zero dependencies, MIT licensed.
Every tool application looks the same: icon rails down the sides, panels you resize, and tabbed documents in the middle that you drag around. Everyone rewrites it, badly, on every project.
panels supplies that chassis once and for all. It is headless: the mechanics come with it, the appearance stays yours.
8 kB gzipped, zero dependencies, MIT. That weight was chosen at design time.