Unplugin is a unified plugin system for various build tools, including webpack, Rollup, Vite, esbuild, and more. It allows developers to write plugins once and have them seamlessly work across different bundlers, simplifying the plugin development and maintenance process. This eliminates the need to create separate plugins for each build tool, boosting efficiency and reducing code duplication. Unplugin streamlines the integration of custom functionalities into the build pipeline across diverse JavaScript and TypeScript projects.