The early combination of the graphical interface, the Clipboard, and multitasking yielded a productivity-boosting feature -- the ability to see and move content between two or more apps on the screen at the same time. The ensuing decades have seen variations that included virtual desktops and "snapping" windows to fill half of a display. But it's long been established that we can realize further productivity gains by using multiple monitors at once. Particularly these days when we constantly need to refer to references on the web or in apps such as Slack, the need for a second screen is more prevalent than ever, and there are a host of options depending on how large a display you're looking to add.
Option 1: Smartphone mounts
Microsoft, Apple, and PC vendors all have ways for your PC and smartphone to work together, but what if you physically want to link them to use your smartphone as a webcam (using apps such as DroidCam and EpocCam), teleprompter, or just monitor some social feed? TenOne Design's Mountie comes in two flavors -- one designed for smartphones and one designed for small tablets. A recent Kickstarter project aims to provide another option. RollingSquare's Edge isn't designed for something as large as a small tablet but can accommodate a few other options, such as a MagSafe adapter and its own video light.
Option 2: Tablet (or Chromebook)-as-Display
There's been much written about the merits of the laptop versus the tablet, but some tablets can also be used as external displays. If you're running a recent Mac and iPad, Apple's solution is Sidecar, which lets you extend your desktop onto something as large as the iPad Pro's 12.9-inch expanse. Samsung also allows its Tab S series to function as an external display on Windows devices. For everyone else, there's Duet Display, which allows a Mac or Windows PC to use an iPad or Android tablet as a second screen using a USB-based driver or wirelessly. The Android support extends to Chromebooks that support Android apps. It's a great use for an older Android tablet that can no longer access the latest apps.
Option 3: USB-C portable monitors
Portable monitors based on the DisplayLink standard have been around for many years, but they require a driver. Increasingly, ultra-slim monitors are being based on USB-C that can deliver video and power (although some still support HDMI). Products offer varying display sizes ranging from about 9 inches to 17 inches, HD and 4K resolution, and whether the display supports touch. A few displays also include a battery so they can be used as a standalone external display for a console for a few hours.
Among PC brands, ASUS and Lenovo -- veterans of DisplayLink primacy -- offer products, as do at least a half-dozen lesser-known brands such as Lepow, Desklab, and Vankyo. Note that these products will burn through laptop batteries, so it's best to use them with the laptop plugged in or connect them to a battery pack that supports USB-C Power Delivery.
A space-saving twist on the portable monitor is from MobilePixels. Its Duex add-on, available in 12.5-inch and 13.3-inch variations, attaches magnetically to the cover of your laptop and offers a slide-out display that can be tilted forward a bit. The company also offers a kickstand accessory, so you can use the Duex display as a more traditional USB monitor, and the larger Plus version can also be used in portrait orientation.
Even though the new generation of Duexes (Duexen?) are lighter than its earlier products, they add significant weight and thickness to the laptop and the magnets will prevent convertibles from 360-degree hinge rotation. In addition, there's no storage or attachment option for the USB cable needed to drive the monitor. However, if your work almost constantly demands two displays, it could be a good option. MobilePixels has also been readying a two-screen variant of the slide-out display called Trio (for the three total screens that include the laptop's internal display).
Option 4: Desktop monitors and all-in-ones
If you regularly need to connect a laptop to a second display at a fixed location, the venerable desktop monitor using HDMI, DisplayPort, or USB-C is at the ready. But if that space is used by yourself or another, it may make sense to have an all-in-one PC like Apple's M1 iMac or HP's just-announced Elite Pro all-in-one . While Windows PCs, unlike Chromebooks, can't be used as USB-C monitors, some all-in-ones have HDMI-in ports so you can take advantage of their screens from your laptop. Just be sure you have a USB-C-to-HDMI adapter if your laptop lacks an HDMI port as many slim modern models do.
Option 5: Augmented reality
If you have a bit more time than space and don't mind bending a bit of both, a new generation of smart glasses such as Lenovo's ThinkReality A3 can connect to your PC and provide multiple monitors in space without your having to take up an extra inch of a surface. Lenovo says its multi-monitor mode was developed with workspace-fluid professionals who might find themselves in locations where there's no room for a traditional display. In contrast, hooking the same headset up to a Motorola smartphone will create a more typical AR experience. The ThinkReality A3 is due to ship later this year.
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