By default, VirtualBox is the default provider for Vagrant. VirtualBox is still the most accessible platform to use Vagrant: it is free, cross-platform, and has been supported by Vagrant for years. With VirtualBox as the default provider, it provides the lowest friction for new users to get started with Vagrant.
However, you may find after using Vagrant for some time that you prefer
to use another provider as your default. In fact, this is quite common.
To make this experience better, Vagrant allows specifying the default
provider to use by setting the
VAGRANT_DEFAULT_PROVIDER to the provider you wish to be the
default. For example, if you use Vagrant with VMware Fusion, you can set
the environmental variable to
vmware_desktop and it will be your default.