App UI styles: 12 interface languages from Palm OS to Liquid Glass
Compare twelve sourced app and operating-system interface languages, including Aqua, Metro, Material Design, Fluent 2, HarmonyOS and Liquid Glass.
What qualifies
The entries here are not generic UI components. Each one has a repeatable visual grammar tied to a documented platform or design system, and enough visible character to be recognised across more than one screen. the five-entry standard
What this guide leaves out
Card UI, command palettes and mobile-first design solve grouping, access and process. They can be rendered in any of the visual languages below, so they remain supporting terms rather than styles.
Supporting terms: Card UI / Command Palette / Mobile First
Desktop metaphors and early personal devices
These interfaces made unfamiliar computers legible through windows, objects, texture and unusually strict constraints.
580
CDE Interface
CDEインターフェース / 1993–2000s
The Common Desktop Environment unified UNIX workstations through Motif-derived bevels, a persistent Front Panel, workspace switching and low-color icons, making different hardware feel like one workplace.
Visual cues: Box-like Front Panel along the lower edge / Raised buttons and recessed fields made from paired light and dark borders / Low-color pixel icons with dark outlines / Persistent buttons for switching among workspaces
599
Palm OS Interface
Palm OSインターフェース / 1996–2009
Palm OS turned a tiny monochrome screen, stylus and strict memory limits into a consistent pocket work tool through the Title, Category menu, Command Bar, hardware buttons and Graffiti writing area.
Visual cues: A roughly 160 by 160 low-resolution monochrome screen / Title at upper left and Category pop-up at upper right / A Command Bar rising from the lower edge and four application buttons / Thin one-bit icons, rules and the Graffiti input area
399
Aqua
アクア / 2000–2014
Mac OS X's design language of buttons you want to lick. Jelly gloss, pinstripes, deep shadows and the genie effect staged digital components as objects you could touch, and set the terms for UI throughout the 2000s. What the web made of it with images is Web 2.0 Gloss.
Visual cues: Gel-gloss buttons / Pinstriped grounds / Deep drop shadows / Metaphors of water and light
581
KDE Oxygen
KDE Oxygen / 2006–2014
Oxygen unified KDE 4 applications, workspace and icons through clear blue, soft gray, fine outlines and icons that seem to rest on a shared shelf, bringing lightness to an information-dense desktop.
Visual cues: Pale-gray chrome with blue selection and restrained gloss / Dimensional icons with one-pixel edges and a lower shelf shadow / One upper-diagonal light source across materials / Toolbars and docks grouped by fine separators
Systems built for products at scale
Choose among these by platform, motion model, density and the amount of brand expression allowed inside a shared component language.
402
Metro
メトロ / 2010–2015
Windows Phone's flat language, which cast type rather than icons in the lead role. Large typography, flat-color live tiles and layouts that run off the edge of the screen transplanted the clarity of transit signage into UI, opening the flat era ahead of iOS 7.
Visual cues: Type as the hero / Flat-color tiles / Compositions running off-screen / Chrome eliminated
472
Material Design
マテリアルデザイン / 2014–
A design system that reduces the physical metaphor of paper and ink to rules of shadow and overlap. Elements are given elevation, shadow states the hierarchy, and motion carries physical cause and effect. It became the model for UI design being distributed as a system. The 2021 revision added colour derived from the device wallpaper, so the palette differs from one user to the next.
Visual cues: Hierarchy and shadow expressed by elevation / Surfaces overlapping like sheets of paper / Motion that shows cause and effect / A standardized unit of spacing
562
Material You
Material You / 2021–
Material You makes adaptability itself consistent: dynamic color, generous shapes and personalized motion vary by person while semantic roles stay stable.
Visual cues: Harmonized colors derived from wallpaper / Large rounded cards and controls / Selection changes both color and shape / Broad spacing and large display type
118
Fluent 2
フルーエント2 / 2022–
Tokenizes color, type, spacing, radius and depth, deploying Solid, Acrylic, Mica and Smoke materials by role across Microsoft products.
Visual cues: Mica and Acrylic / Neutral tonal hierarchy / Soft corner radii / Tokenized depth
Contemporary depth and cross-device continuity
These systems use layers, blur, light and responsive surfaces to maintain one identity across phones, desktops and connected devices.
401
Aero
エアロ / 2006–2012
The translucent glass UI of Vista and 7: frosted window frames, live thumbnails and GPU-composited depth making 'through glass' the OS's standard vocabulary.
Visual cues: Frosted frames / Reflections and highlights / Live thumbnails / GPU-composited depth
582
GNOME Clearlooks
GNOME Clearlooks / 2005–2011
GNOME 2.12's standard theme made GTK applications friendly and simple through pale-gray windows, blue selection, restrained gloss and firm boundaries.
Visual cues: Pale-gray surfaces with blue selection bars / A quiet highlight only along button tops / Tabs and fields with restrained rounding / Small GNOME icons and a concise two-level hierarchy
601
HarmonyOS Design
HarmonyOSデザイン / 2019–
Huawei's visual language reorganizes cards, spacing, arcs, variable type and translucent light materials across different screen sizes and connected devices, favoring continuity of information and action over one fixed screen.
Visual cues: Large rounded cards grouping information by function / Wide space on light fields with a few saturated accents / Arcs, concentric circles and gentle scaling for operation states / Cards and variable type recomposed to suit device size
117
Liquid Glass
リキッドガラス / 2025–
Unifies the floating control and navigation layer as a fluid glass material that refracts and adapts to the content beneath.
Visual cues: Dynamic refraction / Concentric corner radii / Floating control layers / Reflected background color