CSS Glassmorphism Generator: Backdrop Filter and Border Illumination Code

Adjust blur, RGBA opacity, border glow, and shadow depth. See the frosted glass effect live and copy cross-browser CSS in one click. 100% client-side.

Glassmorphism Preview
Frosted Glass UI
Drag the sliders to see real CSS backdrop blur, opacity, border glow, and shadow depth applied live to this card.
See the Effect
Controls Dashboard
Backdrop Blur 12px
Transparency / Opacity 18%
Base Color #FFFFFF
Click to pick any color. Alpha is controlled by the Opacity slider above.
Border Illumination (Glass Edge) 35%
Drop Shadow / Depth 32px
Compiled CSS Output
Key Terms Explained
Glassmorphism
A UI design aesthetic that recreates the visual properties of frosted glass: translucency, blur refraction on background content, and a thin luminous border edge.
Backdrop-filter
A CSS property that applies a graphical filter (such as blur, brightness, or contrast) to the content rendered behind an element, not to the element itself.
RGBA Color Space
An extension of RGB that adds a fourth channel, Alpha, to control transparency. Values range from 0.0 (fully transparent) to 1.0 (fully opaque).
Alpha Channel
The transparency channel in an RGBA or HSLA color value. A value of 0.0 is invisible; 1.0 is fully solid. Glass effects typically use alpha values between 0.08 and 0.25.
CSS Box-shadow
A CSS property that attaches one or more shadow effects to an element box. Used in glassmorphism to add depth and separation from the background layer beneath the card.
Border Illumination
A design technique using a 1px solid semi-transparent white border on a glass card to simulate the physical light-catching edge of a real piece of glass or crystal.
WebKit Prefix
The -webkit- vendor prefix required by Safari for certain CSS properties like backdrop-filter. Always pair -webkit-backdrop-filter with the standard backdrop-filter for full browser coverage.
Z-index
A CSS property that controls the stacking order of positioned elements. The glass card must have a higher z-index than background layers, and the background must be visible beneath it for the blur to render.

The Complete Guide to CSS Glassmorphism

Glassmorphism took the design world by storm when Apple introduced a system-wide frosted glass aesthetic in macOS Big Sur and iOS 14. Today it is one of the most searched CSS techniques for landing pages, dashboards, and modal overlays. This guide explains exactly how it works, how to use this generator, and how to avoid the common pitfalls that make glass effects look flat or unreadable.

How to Use This Glassmorphism Generator

Start by looking at the Live Preview panel on the left. The animated gradient canvas behind the glass card is intentionally complex - it contains multiple overlapping color orbs and a shifting hue animation so you can see the blur refraction working in real time. As you move any slider, the glass card and the CSS output update instantly.

Backdrop Blur controls the pixel radius of the blur filter applied to the background content. Values between 8px and 20px produce the most realistic glass feel. The Transparency / Opacity slider drives the alpha channel of the background-color - keep it low (10%-25%) for authentic glass. The Base Color picker lets you shift the glass tint from cool white to dark obsidian or any custom color. Border Illumination sets the opacity of the 1px glass edge border. Drop Shadow / Depth controls the box-shadow spread to lift the card visually off the background.

Why Glassmorphism Requires a Complex Background

The backdrop-filter blur effect is only visible when there is contrast and variation in the content directly behind the element. If you place a glass card over a solid-color background, the blur has nothing to act on and the card simply looks like a box with a colored background. This is why the preview canvas uses a layered multi-color gradient: it guarantees the blur effect is always perceptible no matter what slider values you choose.

Cross-Browser CSS: The -webkit- Rule

Safari requires the -webkit-backdrop-filter vendor prefix to render the blur effect. Chrome, Edge, and modern Firefox do not need the prefix, but including it first causes no harm. Always output both declarations in this order: -webkit-backdrop-filter first, then the standard backdrop-filter. This generator does that automatically in the compiled CSS.

Frequently Asked Questions

Glassmorphism is a UI design trend that mimics the look of frosted or tempered glass. It combines a semi-transparent background using rgba() colors, a backdrop-filter blur that refracts the content behind the element, a thin semi-transparent border to simulate the physical edge of glass, and a subtle box-shadow for depth. The result is a layered, modern aesthetic popularized by Apple's macOS Big Sur and iOS design language.
As of 2024, backdrop-filter is supported in Chrome, Edge, Firefox (version 103+), Safari, and all modern mobile browsers. Safari requires the -webkit-backdrop-filter prefix, which is why you should always include both backdrop-filter and -webkit-backdrop-filter in your CSS. The only notable gap is older Firefox versions before 103, which required enabling a flag. For the widest coverage, always include the -webkit- prefixed declaration first, followed by the unprefixed standard property.
Text legibility on glass cards depends on contrast. Use dark, high-contrast text on light glass cards, or bright white text on darker glass surfaces. Adding a very subtle text-shadow (such as 0 1px 2px rgba(0,0,0,0.3)) helps text pop against the blurred background. Avoid placing glassmorphism cards over backgrounds with large uniform color blocks - the blur effect is most readable when the background has distinct color variation. The WCAG 2.1 AA standard requires a minimum contrast ratio of 4.5:1 for normal text.
The thin border on a glassmorphism element simulates the physical edge of a real piece of glass, which catches and reflects light differently than the flat surface. Without a border, the glass card blends into the background and looks flat. A 1px solid border using rgba(255,255,255,X) creates a faint highlight along the top and left edges that the eye reads as a three-dimensional glass surface. Higher opacity values make the edge glow effect more pronounced.
The CSS opacity property makes an entire element and all its children transparent, including text and icons. backdrop-filter, by contrast, only affects the rendering of content behind the element - the element itself remains fully opaque. For glassmorphism, you control surface transparency through the alpha channel of the background-color (rgba), not through opacity. This way the glass card's background is semi-transparent while text inside the card stays crisp and fully readable at 100% opacity.