Sorry for being out of commission so long folks! But now I’m back and here to present to you another fantastic App of the Week! This week, I’m covering the Unarchiver, a free, fantastic archiving utility that tightly integrates with Finder and handles all of your uncompressing needs.

Platform Availability: OS X 10.4 and up

Cost: Free! If you like the Mac App Store’s interface, get it here. If not, download it directly from developer Dag Agren’s website.

What it is: The Unarchiver is an archiving utility that is much more robust than Mac OS X’s built-in archive utility. Open an archive, and the Unarchiver will come to life, uncompressing your desired file(s), and then automatically going away so it doesn’t use up any system resources.

How does it work: Install the program, and then it will work in the background whenever necessary. Let’s say you want to uncompress a .ZIP file: simply open the file, the Unarchiver will work its magic, and it will spit out the archived file wherever you want.

Features: Beautifully Simple UX – Unlike similar uncompressing software on Windows like 7-Zip that have ugly, horrible user interfaces, the Unarchiver stays out of your way until you need it. Even when it’s active, all that’s noticeable to users is a small progress bar, outputting the archived file after it’s done. It does what it needs to without barraging you with unnecessary options. Like many other Mac Apps, there’s an emphasis on simplicity and elegance that I really enjoy.

Huge File Format Support – The Unarchiver supports many of the most popular compression formats like Zip, RAR, and 7z. But it also supports more obscure file formats like XAR, RPM, and NDS. I’ve yet to find an archive this program can’t uncompress, and I doubt you will either.

Multi-file archive support – One of the most annoying things about Mac OS X’s built-in archive utility is that it can’t handle archives split into multiple files whatsoever. With the Unarchiver, just download every part of the archive, and then open whichever file in the collection you want. The Unarchiver will automatically piece together the archive and uncompress everything perfectly.

Password Support – Sometimes, the archives I download will be password protected. In those instances, the Unarchiver pops up a simple dialog box to enter the password, then goes about its business uncompressing just as usual.

The Competition: Here are two apps that are great in their own right:

Keka – Free, Mac OS X 10.5 or higher – Download it here.

Entropy – $19, Mac OS X 10.6 or higher – Download it here.

Entropy gives you a lot more customization over viewing and exploring your archives à la 7-Zip. Unfortunately, it also costs $19. As for Keka, it’s another free unarchiving utility that can also compress files/folders into a whole bunch of different formats. It also integrates very well into Finder, and gives you some more options like customizing your uncompressing speed. But for basic uncompressing, I feel the Unarchiver does everything Keka can in a much prettier and OS X-centric UX.

Summary: The Unarchiver is one of those applications that doesn’t do much – just uncompressing – but does it very, very well. It’s straightforward, well-designed, and integrates almost seamlessly into Finder. It’s free, so what do you have to lose?

How would you compare The Unarchiver to Keka/Entropy or anything else? Let us know in the comments!