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What file types does Apple’s Archive Utility open?

August 14, 2020

Short version:

As of macOS Catalina (10.15.6), Apple’s Archive Utility will try to open files with the following extensions:

Long version:

This morning I was reading an article about improvements to the Brotli compression algorithm, and found myself wondering: “What compression formats does Apple’s Archive Utility support by default?”. Searching Google didn’t immediately turn up anything (something I’ve been finding more and more recently), so I wondered if there’s a way to inspect the application to find out what it supported.

There was a Super User answer that pointed me in the right direction, but Archive Utility didn’t have an Info.plist with the file information. What it had instead was a bunch of icons that listed the extension names for supported files. It’s not 100% clear if this list is exhaustive, but it’s good enough for me.

Archive Utility's Resources folder

You can find this folder here:

/System/Library/CoreServices/Applications/Archive\ Utility.app/Contents/Resources

After finding the list, I fell down a rabbit hole of investigating seldom-used compression formats. I’ve added links above to Wikipedia pages for all the formats I could find. The .bin link is a general one, as I’m not sure exactly which format is supported here. The .aar, .as, and .uu formats were unknown to me, but I’m pretty sure the links are correct for these. The one standout was .yaa, which I’d also never heard of. It appears to be Mac-specific. There’s a man page for it (man yaa in a Terminal window) which provides a bit more detail. It seems it was added in High Sierra.

I probably shouldn’t find this surprising, but StuffIt files (.sit, .sitx) aren’t supported by this utility. StuffIt, though now discontinues, is still a commercial project. But those archives are still so strongly linked with classic Mac OS that it’s hard to see .hqx in the list without immidiately thinking of .sit.

While I’m on the topic, there’s a great list of archive formats on Wikipedia as well. I got immediate waves of nostalgia from seeing .arj and .lha in that list.