When I started developing Arq it was partly because I couldn’t find an existing online backup offering that gave me enough control. I wanted to control exactly which files would be backed up, and I didn’t want to be constrained by rules that many of the “unlimited backup” offerings had like excluding network drives, excluding applications, etc.
So Arq lets you back up anything you want. But then the question is, what should you back up? The following is my suggestion for a basic backup of your files on your Mac.
Basic Backup Using Arq
When you first install and launch Arq, it asks your for your Amazon S3 “keys” and a few other things. Then it asks if you’d like to choose your own files for backup, or back up your home folder minus a few unnecessary items:

If you picked “I’ll manually add folders to back up” and you’ve changed your mind, here’s how to set up Arq to back up your home folder minus the unnecessary items:
1. Add your home folder
Click the + button at the bottom left of the Arq main window.

Pick your home folder (/Users/<yourname>) and click OK.

2. Add some excludes
Click the “Edit Excludes…” button.

Add 3 excludes.

Make sure the first 2 are set to “relative path” instead of “name”.
Click OK.
Backing Up Applications Using Arq
If you want to back up your applications, add the Applications folder.

Many applications put some of their support files in /Library/Application Support, so add that too.

Advanced Backup Using Arq
If you prefer, you pick and choose specific folders to back up instead of backing up your entire home directory.
WARNING: If you choose to do this and you later create a new folder in your home directory and start putting important files in there, you’ll have to remember to add this new folder to Arq or else it won’t be backed up!
I back up the following folders as separate items in Arq:
- Application Support (/Library/Application Support)
- Applications (/Applications)
- Documents
- Library, excluding files/folders named ‘Caches’ and ‘Logs’
- Music
- osaka iPhoto Library (my big iPhoto Library, named after my computer), excluding files/folders named ‘iPod Photo Cache’
- src (my work files), excluding files/folders named ‘build’ and ‘bin’
Time Machine and Arq
Time Machine and Arq are complementary. Backing up using Time Machine to another disk is cheap and fast. If you’re backing up to a Time Capsule via Wifi it’s very convenient because it just happens; there’s nothing to plug in. If you’re backing up to a USB drive, you’ll have to remember to plug in the USB drive periodically. Restoring is fast because you’re reading from a USB disk physically connected to your Mac, or from a Time Capsule over Wifi.
But Time Machine doesn’t cover all cases. If someone breaks in and steals your computer, they may steal your Time Capsule or USB drive as well, and then your files are gone forever. If fire, flood, or lightning strikes, you may lose both your computer and your backups; files gone forever. And if you travel often, you’ll have to bring along your USB drive or Time Capsule, or backups won’t happen until you get home and stay home long enough for a backup to complete.
Arq covers those cases that Time Machine doesn’t. The backups are off site at Amazon’s servers, safe from your theif and your natural disasters. They’re even safe from disaster at an Amazon site because Amazon replicates your data at several sites. And Arq works whenever there’s an Internet connection, so backups still happen when you’re on the road.