Liquid Glass is Apple's translucent interface material. It sits in a layer above your content and lets that content show through.
In May I wrote that it changed everything. I still think it did. But I got the shape of the change wrong, and iOS 27 made that obvious.
I wrote about Liquid Glass as a look you adopt. It is not a look. It is a range, and the person holding the phone sets it.
Apple handed the dial to users and took the off switch away from apps. Those are the same decision.
What iOS 27 actually changed
1. Two presets became one slider
What I said: design for the new material.
What shipped: iOS 27 replaced the Clear and Tinted pair from iOS 26.1 with a continuous slider, in Settings, then Appearance, then Liquid Glass. Apple's default is the midpoint. The slider is offered during setup, so people meet it before they ever meet your app. iPadOS 27 and macOS 27 have the same control.
Do instead: design for the two ends, not the middle.
2. Your opt out is gone
What I said: watch the adoption curve.
What shipped: there is no curve left to watch. On iOS 26 an app could set UIDesignRequiresCompatibility and keep its old appearance. Apple's page for that key now says the system ignores it when you build for iOS 27 or later. Build against the current SDK and you are in the glass.
Do instead: stop costing this as optional work. It is the price of your next release.
3. One default is a sample of one
My May post told designers to audit type on glass and to test against system wallpapers. That was right and far too narrow. The wallpaper is one variable. The slider is another, and it moves every surface at once: notifications, Control Center, Home screen folders, your own overlays. Apple also retuned the default look in this release, so even the middle of the slider is not the picture you signed off in June.
4. Standard components adapt. Your custom glass does not.
Apple is blunt about this. Standard components from SwiftUI, UIKit and AppKit pick up the material and respond to the setting on their own. Anything you built by hand does not. The guidelines ask you to test your own elements, colours and animations across those settings. They also tell you to stop picking a material for the colour it gives you. The setting can change that colour. For clear glass over bright content they suggest a dimming layer at 35 percent.
5. Reduce Transparency is the far end of the same dial
Even at the tinted end, the interface keeps some glass. Two accessibility settings go further: Reduce Transparency, which strips nearly all of it, and Increase Contrast. Most teams file those under compliance and never open them. They are not a special case. They are the last stop on the slider, and your layout has to hold together there.
Where your design has to work
| Setting | What the user gets | What breaks first |
|---|---|---|
| Slider, clear end | Heavy translucency, wallpaper reads through | Text contrast, icon edges |
| Slider, midpoint | Apple's default | Nothing, which is why you stop looking |
| Slider, tinted end | Frosted, still glass | Separation between layers |
| Reduce Transparency | Flat, solid backgrounds | Hierarchy that was carried by blur |
| Increase Contrast | Harder edges and borders | Custom colours chosen for softness |
The audit
Take your busiest screen. Capture it five times: slider at each end, slider at default, Reduce Transparency on, Increase Contrast on. Put the five side by side. If any one of them is the first time you have seen that screen, you have been designing for a default rather than for your users.
The rule outlives Apple. If you ship an expressive material, ship the dial with it on day one, before anyone has to ask. Apple needed two releases to add theirs. I needed one post to notice.
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