Apple introduced a new and really nice feature in Lion called AirDrop. AirDrop makes it much easier to transfer files from one Lion-based Mac to another.

A small digression is in order. Perhaps, Apple File Sharing (AFS) is a bit too complicated for some new or inexperienced users. It requires both Macs to be set up properly in System Preferences -> Sharing -> File Sharing, and the user must know the required username and password on the Mac whose file system is to be mounted.

AirDrop, as an alternative, uses something called Wi-Fi Direct. It’s a fairly new protocol that allows to modern Macs, both with Wi-Fi, to see each other more visibly, connect more easily, and transfer files (or an entire folder) with just a drag-and-drop. They don’t even have to be formally connected to a Wi-Fi network — they can just discover each other’s radio and communicate directly as the protocol implies. Plus, the data is encrypted. Apple has published a list of modern Macs that support Wi-Fi Direct. The oldest Mac goes back to 2008, but the Wi-Fi Direct technology only came into popular use recently.

AirDrop is accessed in the Finder sidebar

Apple posits that this protocol is only available between two Macs when using Wi-Fi because that’s the intended operational mode of Wi-Fi Direct. Lion’s default install is set up that way. However, it’s been discovered* that this protocol can also be used over an Ethernet wired connection. Even better, you can mix and match. That is, one Mac can be on your network via Wi-Fi and the other can be connected via Ethernet. Or both can be wired. That’s particularly helpful for users who have an older Mac (that can still run Lion) but isn’t on the list (above) of Macs that support Wi-Fi Direct.

Here’s how to configure your Lion-based Mac to work on either Ethernet or Wi-Fi:

1. Execute this command in the terminal:

defaults write com.apple.NetworkBrowser BrowseAllInterfaces 1 

2. Then, also from the terminal, kill and restart the Finder:

killall Finder

Even if only one Mac is on Ethernet, this preference must also be set on any Wi-Fi Macs to be used, even if they have the required Wi-Fi hardware. You’ll know you’ve succeeded when you enter AirDrop and both Macs see each other in the AirDrop display.

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* Thanks to TMO reader Mike Weasner for testing and pointing out this capability.