When working in VirtualBox, you may have seen a prompt or noticed a reference to Guest Additions. But what are Guest Additions, and should you use them?
Let’s take a look at what VirtualBox’s Guest Additions do, why you should install them, and how to activate them.
What Are Guest Additions in VirtualBox?
The VirtualBox Guest Additions are extra pieces of software, included with your copy of VirtualBox, that enable better performance and functionality in virtual machines. You install Guest Additions inside the virtual machine to activate this functionality.
As you probably know, VirtualBox is a hypervisor, which allows you to create and use virtual machines. This means that you can install Windows and other operating systems inside VirtualBox and have them think that they’re running on actual hardware.
Read our full guide to using VirtualBox
to get up to speed if you’re not familiar.
However, just because you get a working virtual machine running in VirtualBox doesn’t mean the experience is perfect from the start. There are certain elements of running an OS in an app window that are frustrating.
For example, on your main computer, Windows knows what resolutions it can display using the drivers from your graphics card. A virtual machine can’t do this, though, so it displays in a low resolution (such as 800×600) by default.
The Guest Additions of VirtualBox contain display drivers and other useful tools that make your virtual machine much more usable.
What Do the Guest Additions Do?
Now that we know what Guest Additions are, let’s look at what the VirtualBox Guest Additions actually do for you.
1. Shared Clipboard/Drag and Drop
Chances are that you’ll eventually want to move some content between your virtual machine (the guest) and your actual computer (the host). With the Guest Additions installed, VirtualBox packs a few features to make this easy.
First is the shared clipboard/drag and drop support. This allows you to copy items on one platform and paste them on the other, as well as dragging files between them. To adjust this, select your VM on the VirtualBox home page and choose Settings.
In the General section, switch to Advanced tab and you can choose options for Shared Clipboard and Drag’n’Drop. You can choose Disabled, Host to Guest, Guest to Host, or Bidirectional for both of them.
Unless you have a specific reason to choose something else, Bidirectional is the most convenient.
Once you have this enabled, both copy/paste and dragging will work across systems.
2. Shared Folders
If you’d rather make folders on your host system accessible in the VM, you can utilize shared folders. This Guest Additions feature lets you mount host folders as “network resources” in the guest OS without actually using a network.
To use it, click Settings on a VM and jump to the Shared Folders section. Select the Add Share button on the right side, then choose a folder on your computer to share with the guest.
Give it a name, choose Auto-mount if you want it to connect automatically, and hit OK.
Now, that folder will appear as a network drive in the guest OS.
3. Improved Graphics Support
As mentioned earlier, virtual machines don’t support high-resolution graphics from the start. Once you install the Guest Additions, though, you’ll have full control over the resolution options in the guest OS’s settings menu. For instance, if you have a 1920×1080 monitor, you can display the VM in full-screen at 1080p.
That’s not the only graphical enhancement that the Guest Additions add. Using them, the guest OS’s resolution will dynamically resize as you adjust the VirtualBox window on your computer. This lets you use the VM at any size you like without playing with resolution options.
Finally, with Guest Additions, the guest OS can take advantage of your computer’s graphics hardware. If you’re playing games or using other graphically intensive software in a WM, this makes a huge difference.
4. Seamless App Windows
Another neat benefit of the Guest Additions is a seamless mode. This lets you run app windows from the guest alongside apps from your host OS, so it feels like they’re all part of one system. It’s a lot like how Parallels runs Windows apps on a Mac
To use this mode, press the Host key + L when your virtual machine is in focus. If you haven’t changed it, the default Host key in VirtualBox is the right Ctrl key.
Once you’ve done this, the VM will go full-screen and VirtualBox will remove its background. You’re then free to use its windows with your regular desktop software. Hit Host + L again to turn this off—if it doesn’t seem to work, make sure you select the VirtualBox VM first.
5. Other Benefits of VirtualBox Guest Additions
The above functions are the main features of VirtualBox’s Guest Additions. There are a few other useful perks to installing them, though these are not as generally useful.
One that may affect you, depending on the guest OS, is seamless mouse integration. With most modern OSes, VirtualBox allows you to seamlessly move your mouse between your host and guest system. However, some older OSes require exclusive control of your keyboard and mouse.
If this is the case, your mouse pointer will become “trapped” inside the VirtualBox window after you click inside it. This means that you must hit the Host key (right Ctrl by default) to bring the mouse control back to the host OS.
Otherwise, the Guest Additions bring time synchronization with your host machine, the option for automated logins, and can monitor communications between the guest and host. None of this has much use for the average user.
How to Install VirtualBox’s Guest Additions
It’s easy to install the Guest Additions on your VirtualBox system. In fact, every time VirtualBox receives an update, it includes a new version of the Guest Additions too. You don’t necessarily need to update the Guest Additions every time you update VirtualBox, but Oracle recommends it for best performance.
Keep in mind that the Guest Additions are available for Windows and Linux, but not macOS. You’ll need other workarounds if you’re running macOS in a virtual machine
Install Guest Additions on Windows VMs
To install the Guest Additions for VirtualBox in a Windows VM, boot into your guest OS as normal. On the toolbar at the top, select Devices > Insert Guest Additions CD Image. This mounts a virtual disc to the VM.
When you do this, Windows will respond as if you’ve just inserted a physical disc. If it doesn’t prompt you to run it, open a File Explorer window and go to This PC. You should see a device in the CD Drive named something like VBox_GAs_x.
Double-click this to open the disc’s contents. Inside, run the VBxWindowsAdditions file (or VBxWindowsAdditions-x86 on a 32-bit VM).
From there, simply walk through the steps to install the Guest Additions like you would any other software. After it completes, you’ll be prompted to reboot the VM, which you should do as soon as possible.
Once you’re done, you can go to Devices > Optical Drives > Remove disk from virtual drive to “eject” the virtual Guest Additions disc.
Install Guest Additions on Linux VMs
The process to install VirtualBox’s Guest Additions into a Linux VM is quite similar. Once you’ve booted up, select Devices > Insert Guest Additions CD Image from VirtualBox’s menu bar. Depending on your flavor of Linux, you may see a message to automatically run the CD’s contents.
You can accept this, but if you don’t, you’ll find the CD available on the taskbar in many Linux distros. If it doesn’t appear there, open the file browser and look for VBox_GAs_x on the left sidebar.
On Ubuntu, a Run Software button appears at the top-right of the window. Click this to start the install process, then provide your admin password to continue. A Terminal window will open to keep you updated with its progress.
Once it’s done, reboot the VM and you’re all set. You can then eject the disk using the Devices > Optical Drives > Remove disk from virtual drive option, or by right-clicking it in your OS and choosing Eject.
Guest Additions Make VirtualBox Even Better
As we’ve seen, the Guest Additions make running virtual machines with VirtualBox much smoother. You should always take a few moments to install the Guest Additions when setting up a new VM, as there’s no drawback to doing so.
If VirtualBox isn’t working for you, check out how VirtualBox compares to other virtualization tools