Unlike Apple’s bundled apps in macOS, the great majority of third-party software needs to run on more than just the latest version of macOS. This is a challenge when there’s a major redesign of the interface, as there is in macOS Tahoe. While OS 26 may bring greater consistency across platforms, it’s also important to developers and users that it doesn’t sacrifice consistency between, say, Sequoia and Tahoe.

As I showed recently in my simple little utility DropSum, at times the appearance of windows can be very different between macOS 15 Sequoia and 26 Tahoe. DropSum uses AppKit rather than SwiftUI, and is a little unusual in applying colour to its window. This is used in a popular mechanism to indicate when that window is ready to receive a file being held over it, by changing the view colour from systemOrange to systemGreen. As that coloured view extends over the controls in the window, I have had to be careful to ensure those controls remain readable in both appearance modes, with the Reduce transparency and Increase contrast settings in Accessibility settings, and across recent versions of macOS. That hasn’t proved easy, so what you see below appears to be the best compromise I can achieve. DropSum doesn’t alter its settings or behaviour between different versions of macOS, instead relies on the host API’s appearance modes and Accessibility settings.

Although I have confirmed the observations below on individual systems, to make comparison easier here each screenshot shows two DropSum windows. The upper is running in a Tahoe beta 7 VM (where the window title is left-aligned), and the lower in Sequoia 15.6.1 on the host (where the window title is centred).

Light mode

In both light appearance modes, all boxed text is displayed in black on a white background, making their contents and controls clear. There are marked differences in the hues seen, though, with both systemOrange and systemIndigo (chosen for better contrast in labels) being more intense in Tahoe than Sequoia. As expected, Tahoe’s controls are slightly larger, and the corners of all four text boxes are rounded rather than square.

Reducing transparency made little difference in either rendering, merely whitening the window title bar.

Increasing contrast changes the intensity of some colours. In Sequoia, systemOrange is lightened, and in both windows the traffic light buttons at the top left, and the Clear button, are darkened. Otherwise the most obvious effect is the outlining of all components, including each of the controls.

Apps built to support macOS 26 thus appear consistent between macOS 15 and 26 when used in light mode.

Dark mode

Most apparent here are the contrasting effects of dark mode on the background of the four text boxes. In Sequoia, their background is the systemOrange of the coloured view, but in Tahoe it’s black. The latter makes the text contents more readable, while unselected text in Sequoia is more difficult to read.

Increasing contrast has different effects on colours when in dark mode. In Sequoia all colours including the systemOrange view become slightly lighter, whereas in Tahoe the contrast of some is enhanced, with black becoming blacker and white whiter, but there’s little discernible change in systemOrange, which remains significantly more intense than in Sequoia. systemIndigo is rendered lighter though, making it more difficult to read against the systemOrange background.

Reduce transparency

Apple describes this effect as replacing “the transparent effect used on some backgrounds in macOS with a solid background to improve contrast and readability.” In both Sequoia and Tahoe, and in both appearance modes, the only effect observed is a lightening of the window title bar, as the rest of the window is already opaque.

Increase contrast

Apple describes this as increasing “the contrast of items on the screen (such as borders around buttons or boxes) without changing the contrast of the screen itself.” Although the borders are the most prominent effect in both versions of macOS and both appearance modes, there are also colour changes that aren’t consistent between Sequoia and Tahoe.

Conclusions

• Appearance modes in Tahoe exhibit different behaviours from those in Sequoia, most markedly in dark mode. In this example, Tahoe has the effect of enhancing readability in dark mode.
• Colour rendering of systemOrange also differs between Tahoe and Sequoia.
• Reduce transparency has little effect other than making transparent views opaque.
• Increase contrast primarily adds black (light mode) or white (dark mode) borders to controls, but its small colour changes, as seen here in Tahoe, may impair readability.
• Designing an interface that behaves consistently in both macOS Tahoe and older versions of macOS is a challenge that may not always work out. Developers need to assess their app’s human interface thoroughly in multiple macOS, appearance modes and Accessibility settings.

As we near the end of Tahoe’s incubation period, and Apple’s engineers code its last fixes and tweaks ready for its launch in just a few weeks, I’d like to reflect on what macOS 26 has to offer beyond its marketing headlines.

While there are several worthwhile new features such as the Phone app, Magnifier, and live translation, there’s nothing to compare with the fundamental changes in recent versions of macOS that brought the SSV, Shortcuts, System Settings and Apple Intelligence. Instead Tahoe is overwhelmingly about its human interface.

Every new design of the Mac’s operating systems that I can recall has elicited outcry from many. Understandably, the majority almost invariably want constancy, the same Finder and app icons that we’ve become so familiar with. It’s only human. It’s also a sure route to what others will condemn as stale, as it hasn’t been refreshed for so many years.

Personally, I don’t like to see a design on my Mac. If I notice it, then it’s a distraction. I’d much prefer to have an interface as clean as the whistles of the late Classic Mac OS period: lean, purposeful and lacking in visual trickery or frippery. But I accept that, without all the adornments and animations, many today would wonder why their Mac needed a GPU. I confess that I was never a fan of the original Aqua interface either. Given that its declared goal was to “incorporate colour, depth, translucence, and complex textures into a visually appealing interface”, I wonder whether much the same could be said of Tahoe.

Perhaps the most striking feature of this redesign is its lack of contrast between elements and tools in window controls and their contents, whether its appearance is set to light or dark mode, or one of its new in-between variants. You can see this clearly in most screenshots of Tahoe, such as those posted by Apple, and as far as I can see it hasn’t improved during beta-testing. This is also universal, and isn’t confined to apps using the more novel SwiftUI, although I have to keep pinching my thigh to remind myself that SwiftUI is now six years old, only two years younger than APFS. The contrast in stability and maturity between the two couldn’t be greater.

You can of course ‘improve’ contrast by enabling Reduce Transparency in Accessibility settings, but in doing so you lose most if not all of Tahoe’s Liquid Glass effects, as they depend on the transparency you’ve just turned off.

Transparency is a good example of design being given priority over readability or content. Because the appearance of the upper layer containing controls or content depends on what is underneath, it’s down to chance whether the greyed text you’re struggling to read happens to be over a background that further reduces its contrast. In the worst case, you could find yourself having to move a window so you can read part of it clearly, not a sign of a good human interface.

My other major concern with Tahoe’s new look is that it seems not to recognise the differences between Macs, iPads and iPhones, in terms of displays, input controls, and apps. Rather than sameness, I’d much rather have consistency that recognises the difference between manipulating Xcode’s compound windows containing dense structured text on a 27-inch display, and checking a family photo filling the 6.1-inch display of an iPhone.

One of my favourite controls in macOS is the Combo Box, a versatile and elegant hybrid of the popup/dropdown/pulldown menu/button and a text entry box. I can’t recall seeing one used in iOS, as it would be clumsy and inappropriate. It’s well supported for macOS in AppKit but hasn’t yet been implemented in SwiftUI. If controls are going to be common across all Apple’s operating systems, then macOS is about to lose one of its best.

It seemed only appropriate that, in the weeks before Apple releases OS 26 across Macs and devices, Tim Cook should go to the White House to pay its corporate tribute in a block of materialised Liquid Glass mounted on pure bling. But the image that I keep thinking of in fear, is that of Elon Musk demonstrating the resilience of his Cybertruck’s window by throwing a metal ball at it, in November 2019. I just hope Tahoe’s Liquid Glass doesn’t go the same way.