---
name: Mica
slug: mica
category: aesthetic
status: published
created: 2026-08-21T00:00:00.000Z
modified: 2026-08-21T00:00:00.000Z
definition: Fluent's opaque app background material, subtly tinted with the
  user's desktop wallpaper colour and going neutral when the window loses focus.
aliases:
  - name: mica material
    source: fluent
  - name: Mica Alt
    source: fluent
  - name: wallpaper-aware background
tags:
  - depth
  - platform-registers
  - theming
relations:
  contrastWith:
    - glassmorphism
    - material-you
    - windows-aero
  variantOf: []
  partOf: []
  seeAlso: []
implementations:
  - system: fluent
    name: Mica
    url: https://learn.microsoft.com/en-us/windows/apps/design/style/mica
sources:
  - title: "Microsoft Learn: Mica material"
    url: https://learn.microsoft.com/en-us/windows/apps/design/style/mica
  - title: "Microsoft Learn: Materials used in Windows apps"
    url: https://learn.microsoft.com/en-us/windows/apps/design/signature-experiences/materials
demo: inline
exhibit: false
useWhen: an opaque window background tinted by the wallpaper
---

Mica is the background Windows 11 gives to long lived windows: Settings, File Explorer,
the apps you leave open all day. It is opaque, so nothing behind the window is ever
legible through it, and it is personalised, because its neutral is mixed with a colour
taken from the desktop wallpaper underneath. Move the window across a wallpaper and the
tint shifts with it. Leave the window and it drops the tint entirely, falling back to a
plain neutral fill, which is how a screen full of windows says which one is listening to
your keyboard. Mica Alt is the same material with the wallpaper pushed harder, meant for
apps whose title bar carries tabs and needs to separate from the commanding area below.

The Fluent material family is worth keeping straight, because the three names are
routinely used as if they meant one thing. Mica samples the wallpaper once and paints an
opaque fill from it, so what you see through a Mica window is nothing at all. Acrylic is
translucent and blurs live, recomputing as content moves behind it, which is why Microsoft
reserves it for transient surfaces such as flyouts and menus rather than for the app
backdrop. [Glassmorphism](/glassmorphism) is the genre both of those belong to as a look,
the general translucent blurred panel that arrived in interface fashion around 2020.
Mica is the odd one out of the three, since it is the only member that is not see through.

The sampling rule is the whole engineering argument. A live blur has to be recomposited
whenever anything under it moves, and an app backdrop is the largest surface in the
window, so the cost lands on every frame for the whole life of the app. Mica captures the
wallpaper once, which is why Microsoft describes it as designed for performance and why it
is the material recommended for backdrops while acrylic is not. Mica also knows when to
stop: it collapses to a solid fill when the user turns transparency off, when battery
saver is on, on low end hardware, in High Contrast mode, and whenever the window is
inactive. Every one of those is the material admitting that personalisation is the first
thing worth spending.

Borrowing the idea outside Windows is harder than it looks, because the web has no access
to the desktop wallpaper, and an opaque fill tinted by an image you cannot read is a
strange thing to fake. What does travel is the principle: derive the app's base surface
from something the user already chose, keep it opaque so text contrast is fixed rather
than dependent on scroll position, and let focus be the thing the colour reports. That
last part is the piece most often skipped, and it is the one carrying real information.