Pixel counts have exploded over the last few years, a trend that started in mobile devices but has quickly spilled over to televisions and PC monitors. While most still use a 1080p display, a number of excellent 4K monitors are now available, and the first 5K models have hit store shelves.

The dramatic, sudden rise in resolution hasn't been an easy transition for Windows to handle. The OS has long offered scaling options for users, but the range of resolutions has never varied this much. Windows 7 and even 8.1 often struggled to cope. The result? Jagged, heavily aliased text, ugly stretched icons, and wasteful interface elements. Does Windows 10 do better, or is Microsoft still operating in a 1080p world?

Turn it up to 400 percent

Officially, the specifications of Windows 10 display an impressive array of customization. The operating system is designed to work on phones with screens as small as four inches, or on the 80-inch Microsoft Surface Hub.

In the PC realm, the OS supports devices with a minimum display size of eight inches and resolution of 800 x 600 pixels. There's no upper bound to the display size, and the maximum supported resolution is 8K. The company recommends a minimum display size of 27 inches for 8K to be usable. Of course, there's currently no such thing as a 27-inch, 8K display, so no one can test that limit just yet.

Microsoft did make an effort to keep up with high-resolution displays in Windows 8.1, as it added scaling as high as 200 percent of the standard. With Windows 10, though, the company has lept forward with necessary aggressiveness. The maximum scale is now 400 percent of normal -- high enough to look comically large even on Dell's 5K monitor.

More precise changes can be made by delving into the control panel, where it's possible to set a custom scaling level. The built-in levels, which change in 25 percent increments, seem adequate for any use we can imagine, but it's nice to know the option for further customization is there.

Users can also now, for the first time ever, dictate different scaling for each monitor. That's important for power users, particularly those who have a powerful laptop and an external monitor. Using the Dell XPS 13 with its optional 3,200 x 1,800 display alongside a 1080p external monitor was a pain in older versions of Windows. Scaling the interface so it's readable on the laptop would make icons and text too big on the secondary monitor. Windows 10 finally fixes that issue.

As a final touch, Microsoft offers lockscreen and wallpaper photos that look clear on UltraHD displays. I'm not sure if the largest versions are 4K, but they look close. The Windows Spotlight images that appear in the login screen by default are particularly sharp. In Windows 8.1 many of the default wallpaper and login images looked a blurry mess on UltraHD displays.

Bigger, and more beautiful

There's more to scaling than a slider, however. Blowing up an icon by 200 percent is bound to cause image quality problems. You can observe this yourself with any image editor. Load a photo, blow it up by twice its size, and observe the result. It will likely seem a bit fuzzy compared to the original, to say the least.

There are ways to combat this, however, and Microsoft has made the effort to modernize its fonts and icons so they better handle very high resolutions. As a result, most of the Windows 10 interface appears absolutely crisp on a 27-inch 4K or 5K display, or on a 15-inch 4K display. I'm not just talking about the "metro" interface -- this extends over to almost all desktop elements. It's possible to find exceptions, such as the Command Prompt, which looks a bit of a mess, but for the most part Windows 10 looks brilliant.

Take this comparison of the Control Panel, for example. Windows 8.1 is on the left, and Windows 10 is on the right. Both screenshots were taken on a 27-inch 4K monitor with DPI scale set to 200 percent of normal.

Quite a difference, isn't it? In Windows 8.1 the text is obviously aliased, and as a result it doesn't look sharp. On Windows 10, though, the text appears immediately crisp. It's almost impossible to see distinct pixels in the font at 4K resolution when viewed from a normal distance. On Dell's 5K monitor it's literally impossible to see distinct pixels in the font from 20 inches away -- unless you have superhuman vision.

This difference extends even to the Start Screen. Windows 8's Metro design was built with high resolutions in mind, but when pushed to 4K, it did show some signs of breaking down. Icons could appear blurry, and text a bit imprecise. Again, the image below shows Windows 8.1 on the left, Windows 10 on the right.

Clearly, another significant improvement. Microsoft has put a lot of effort into high-DPI for Windows 10, ensuring that fonts scale well and that high-resolution icons exist for extreme displays, and the work has paid off. Windows 10, unlike 8.1, does justice to UltraHD monitors.

It's not all sunshine

That's not to say high-DPI scaling is perfect. As mentioned, there are flaws within the Windows interface. You generally won't find them, but you can drudge them up if you visit some of the older, more obscure utilities -- such as Computer Management, Task Scheduler and the aforementioned Command Prompt. Indeed, some of these applications appear to have design elements left over from Windows XP.

Third-party apps are the larger issue. Blizzard's Battle.net launcher is a great example. You'd think one of the world's most successful game developers would ensure its launcher is at least usable on high-DPI monitor -- but you'd be wrong. It doesn't scale properly at all, so text looks tiny and is sometimes unreadable. Other applications that trip me up include the free image editor GIMP, and Slack, a collaboration platform.

In fairness to Microsoft, there's only so much it can do to handle third-party applications that haven't been built with UltraHD in mind. Apple is a bit more aggressive in the demands it places on developers, but even OS X users run into applications that don't play well with Retina displays. The only true solution is time; eventually, old applications will fall out of use or be updated, and that'll be that.

A good day for high-DPI

While Windows 10 isn't perfect on an UltraHD display, the experience has come a long way. I'm sincerely surprised, as I didn't think Microsoft could make such strides in so little time.

Even Windows 8.1 is pretty rough on 4K monitors, and doubly so if the 4K panel in question is in a 15-inch laptop instead of a 27-inch external monitor. Yet the new operating system fixes almost all the problems that plagued its predecessor. Text, icons and first-party apps look razor sharp.

If you have a 4K monitor, Windows 10 is absolutely mandatory -- and conversely, if you've been holding off on 4K because of how badly Windows 8.1 handled it, you can now buy that UltraHD monitor you've been dreaming of.

Highs

  • Clearer text at high resolutions
  • More scaling options
  • Better multi-monitor support

Lows

  • Third-party app support is still iffy