egui

egui (pronounced "e-gooey") is a simple, fast, and highly portable immediate mode GUI library written in pure Rust. Created and maintained by Emil Ernerfeldt (@emilk) and sponsored by Rerun, it targets both native desktop platforms and the web via WebAssembly, making it one of the few Rust GUI libraries that works seamlessly across both environments.

What It Is

egui is an immediate mode GUI library — meaning the UI is described and rendered every frame rather than stored as a persistent object tree. Unlike retained-mode frameworks, egui requires no callbacks, no on-click handlers, and no synchronization between app state and GUI state. A button interaction looks like: if ui.button("Save file").clicked() { save(file); }. The library is not a framework; it is a library you call into, giving you full control over the application loop.

The official application framework built on top of egui is eframe, which supports compiling the same app to Web, Linux, macOS, Windows, and Android.

Immediate Mode: Tradeoffs to Know

The immediate mode model has concrete advantages and disadvantages the README documents explicitly:

Advantages:

• No callbacks or event handlers cluttering code flow
• No risk of stale GUI state diverging from app state
• GUI code can live in a simple function — no dedicated UI object required
• Highly interactive UIs can be more performant than retained-mode equivalents

Disadvantages:

• Layout is harder: window sizes must be known before content is laid out, causing occasional first-frame jitter (mitigated via Context::request_discard for a second pass)
• Large scroll areas with many widgets can tax the CPU since layout runs every frame
• Typical CPU cost is 1–2 ms per frame; egui only repaints on interaction or animation

Widget and Feature Set

egui ships with a broad set of built-in widgets and layout primitives:

• Widgets: labels, text buttons, hyperlinks, checkboxes, radio buttons, sliders, draggable values, text editing, color pickers, spinners, images
• Layouts: horizontal, vertical, columns, automatic wrapping
• Text editing: multiline, copy/paste, undo, emoji support
• Windows: movable, resizable, named, minimizable, auto-sized and auto-positioned
• Regions: resizing, vertical scrolling, collapsing headers, panels
• Rendering: anti-aliased lines, circles, text, and convex polygons via the epaint 2D graphics API
• Accessibility: optional integration with AccessKit, enabled by default in eframe, providing native accessibility APIs on Windows and macOS

A community-maintained wiki lists additional third-party egui crates for extended widgets and features.

Integration Architecture

egui is designed to be renderer-agnostic — it produces a triangle mesh each frame that any graphics backend can render. Official integrations include:

• eframe — cross-platform app framework (web + native)
• egui_glow — rendering via the glow OpenGL wrapper
• egui-wgpu — rendering via the WebGPU API (wgpu)
• egui-winit — windowing integration via winit

Third-party integrations cover game engines including Bevy (bevy_egui), miniquad, three-d, and others. The integration surface is intentionally minimal: gather input, call GUI code, handle output, render triangles.

Update: Version 0.36.1

The latest release is 0.36.1, published on August 7, 2026, described as a Sense::drag() bugfix release. The repository remains under active development with the main branch last pushed August 25, 2026. The project has accumulated over 30,000 GitHub stars and more than 2,100 forks, reflecting broad community adoption. egui is dual-licensed under MIT and Apache 2.0.