MicroUI, an immediate-mode UI library written in ANSI C, packs its entire implementation into roughly 1100 lines of source code. The library operates within a fixed-size memory buffer, avoiding any dynamic allocation, which makes it attractive for embedded systems and low‑memory environments. It supplies basic widgets like windows, buttons, sliders, text labels, checkboxes and controls.

Because MicroUI does not perform any drawing itself, it delegates rendering to any backend capable of drawing rectangles and text. This design lets developers plug the library into OpenGL, Vulkan, software rasterizers, or platform‑specific APIs without modification. The API also includes a simple layout system that arranges widgets in rows or columns for flexible UI.

The library ships with a minimal demo that showcases a window containing two buttons, a popup, and a scrollable panel, all defined in a handful of lines. Documentation lives in a usage.md file and a demo directory, guiding developers through the API without imposing a specific graphics stack. Contributions focus on extending controls rather than adding heavy features.

MIT licensed and free to modify, MicroUI’s tiny footprint and deterministic memory usage make it a practical choice for hobbyists building game tools, IoT dashboards, or any application where a full‑blown UI framework would be overkill. The project welcomes bug reports but limits pull requests to core functionality today.