Laptops have become increasingly powerful over the last few years, but there's one compromise that's hard to overcome: a small screen. Unless you're going to carry a 17in monster around - and even a 17in screen is tiny by today's standards - you're forced to work on a display between around 11-15 inches.
So when you're at a desk, it pays to hook up a large monitor to make things a bit easier. And you can even carry on using the laptop screen for extra desktop real-estate.
An increasingly popular option is a portable monitor which you can carry around with your laptop and power from a USB-C port. Lenovo's M14 - shown above - is a good example, and isn't horribly expensive at $199 (around £220 in the UK).
Most laptops have at least one connector that can be used to plug in a monitor, be it HDMI, VGA, DVI, or DisplayPort. Some of the very thin laptops require an adapter as there isn't room for a full-size DisplayPort or HDMI output, and this isn't always supplied in the box.
Although we're talking about laptops, it is just as easy to connect a second screen to a PC: just have a look and see which ports are on the back.
If you haven't already got a screen, then be sure to choose one with an input that matches your laptop's output. Handily, we have a list of our recommendations for the best monitors to buy.
Sometimes it's possible to mix and match some of the digital options. For example, you can convert DVI to HDMI with a basic cable. But you cannot convert an analogue signal (such as VGA) to digital, such as HDMI, without a box of active electronics: any passive cable you find for sale will not work.
The newest laptops may have only a USB-C port. This the same physical connector you'll find on most new Android phones. It's reversible and you can buy a USB-C to HDMI cable, or USB-C to DisplayPort, depending upon which one of these inputs your screen has.
Here's what to look for on both your laptop and screen:
Another option is to use a USB docking station that boasts one or more HDMI, DisplayPort, DVI or VGA port, as well as extra USB ports, memory-card readers, Gigabit Ethernet for wired Internet access, and more.
You connect to the dock with a single USB cable, and immediately gain access to all the dock's ports.
Check if your laptop uses USB-C or the older USB-A (also known as USB 3.0) to choose the right dock. We've tested the best USB-C and Thunderbolt docks. A dock such as Plugable's UD-3900 works well for older USB-A/USB 3.0 laptops: under £100 in the UK and under $90 in the US via Amazon.
How to set up a second screen in Windows
Once you've connected the appropriate wire between your laptop and monitor (and supplied power to the monitor, if required) it's time to configure Windows to use both screens.
In most cases, Windows will automatically detect when a monitor is plugged in and turned on, and duplicate the contents of your laptop screen on it. If you don't see anything on the screen, use its buttons to find the menu and see if you can select the correct video input as not all will automatically switch to an input with a video signal coming in.
Next, right-click on the Windows desktop and choose Display Settings. Or, click Start, Settings and System. Here you'll find options such as orientation, text size and resolution.
How to duplicate or extend the Windows desktop across two monitors
You have various options for what to display on each of the two screens.
• Duplicate: The second monitor mirrors what's on your laptop's screen.
• Extend: The Windows desktop is spread across the two monitors.
• Show only on 1 or 2: Only one of the displays will be used (click Identify to see which is which).
Another way to switch between these modes is to look for a function key on the top row of keys on your laptop which shows two monitors. Press the Fn key and that function key and it should toggle through the various configurations: laptop display only, laptop + external screen, external screen only.
In almost every case, you'll want to pick 'Extend these displays' so you can treat the second monitor as a separate desktop where you can run a different app to the one showing on your laptop screen.
Then, drag monitor 2 in the diagram below the heading 'Customise your display' to where it is physically on your desk. It defaults to the right-hand side of your laptop's screen, which may be ok if that's where you put it.
If the resolution of the monitor is larger than your laptop's, the rectangle will be larger in the diagram - it's nothing to do with the actual size of the monitor.
You can drag the second monitor's icon so the bottom edges line up, or you can have an equal area top and bottom: it's completely up to you. But remember that this will affect how you have to move the mouse between the screens.
Check that the resolution for each screen is set to each monitor's native resolution - you might have to check the specifications if you don't know these figures already.
For screens with high resolutions (mainly 4K monitors), you'll probably want to use the 'Change the size of text, apps and other items' slider to make sure everything is easily readable. Typical settings are 150%-250%.
Once you're happy, click Apply and the changes you just made should be reflected on the monitor connected to your laptop.
And now you can use your connected monitor just as your laptop screen: you can place shortcut icons on it, open apps and even run multiple apps.
If you have one of Apple's MacBook laptops or desktop Macs, see Macworld's advice on connecting a second screen to a Mac.