Blur, tint, and transparency, layered into one effect
A 12px blur with a 35% opacity white tint produces: background: rgba(255, 255, 255, 0.35); backdrop-filter: blur(12px); plus the -webkit- prefixed version for Safari, since that browser support option is checked.
The 'glass' look comes specifically from the combination of two properties working together -- backdrop-filter: blur() blurs whatever is visually behind the element, while the semi-transparent background color (rgba with 0.35 opacity) tints that blurred background, together producing the frosted-glass appearance rather than either property alone.
Opacity and blur interact to control the effect's intensity independently -- a higher opacity (closer to 1) makes the tint more opaque and the underlying content less visible through it, while a higher blur value makes whatever's behind more indistinct, and the two can be tuned separately to taste.
Why this effect needs something behind it to actually work
Needs a backdrop behind the element. Safari still wants the -webkit- prefix when that box is checked. backdrop-filter has nothing to blur if there's no visual content (an image, another colored element, page content) actually positioned behind the element it's applied to -- placed over a plain solid background with nothing else behind it, this effect would show the tint but no visible blur, since there'd be no detail behind it to blur in the first place.
Safari has historically required the -webkit- prefixed version of backdrop-filter even after other browsers dropped the need for vendor prefixes on this property -- including both the standard and -webkit- prefixed lines (as this generator does when the option is checked) maximizes cross-browser compatibility.
This produces one glass-panel effect as static CSS -- if you want the blur or opacity to change on hover or some other interaction, that would need to be layered on with additional CSS transitions or state-based classes beyond this generator's base output.
Related CSS visual-effect tools
For a related but visually different soft-UI effect built from shadows rather than blur and transparency, the CSS Neumorphism Generator covers that distinct aesthetic.
For general CSS filter effects (blur, sepia, grayscale) applied to an element itself rather than its backdrop, the CSS Filter Generator is a related but different tool.
Frequently Asked Questions (FAQ)
Why does the glass effect need both backdrop-filter and a semi-transparent background?
backdrop-filter: blur() blurs whatever visually sits behind the element, while the semi-transparent rgba background tints that blurred backdrop -- the frosted-glass look comes from these two properties working together, not from either one alone.
Why doesn't the glass effect show any visible blur on a plain solid-color page?
Needs a backdrop behind the element. Safari still wants the -webkit- prefix when that box is checked. backdrop-filter blurs actual visual detail positioned behind the element. With nothing but a flat, uniform color behind it, there's no detail to blur, so only the tint would be visible, not the characteristic frosted texture.
Why does Safari need the -webkit- prefixed version of this property?
Needs a backdrop behind the element. Safari still wants the -webkit- prefix when that box is checked. Safari has historically required the -webkit-backdrop-filter prefix even after other browsers no longer needed a vendor prefix for this property -- including both lines maximizes compatibility across browsers.
How do opacity and blur each affect the final look independently?
Higher opacity makes the tint more solid and the content behind less visible through it. Higher blur makes whatever's behind more indistinct and smoothed out. The two can be adjusted separately to fine-tune exactly how 'frosted' versus 'see-through' the effect appears.
Does this generate a hover or animated version of the glass effect?
No, it produces static CSS for one glass-panel state. Adding a hover transition or animated change in blur/opacity would require additional CSS transitions or interactive state classes layered on top of this base output.
