Why Have macOS Updates Gotten So Absurdly Huge?

Mostly, it’s about reliability

Key Takeaways

  • Big Sur slurped down over 50 GB of software updates in a year, compared to 21.5 GB for Mojave.
  • The smallest update size for M1 Macs is about 3.1 GB.
  • Mac software updates are more reliable than ever.
A group of people using laptop computers, as seen from above.

Marvin Meyer / Unsplash

Mac users who pay attention to software updates may have noticed something strange over the past few years: macOS updates have gotten utterly massive. 

On iOS and older macOS versions, software updates would come in at a few hundred megabytes each, perhaps even smaller for basic fixes. But ever since Big Sur, you’re lucky to get anything smaller than 2-3GB a pop, even when the update, itself, only requires a few megabytes. This wastes data and time and—when it’s all added together—a significant amount of energy. So why are they so big? It’s mostly about reliability.

"With Big Sur, Apple not only changed the System volume, so that macOS now boots from a sealed snapshot of the system, but it changed the way that macOS is updated," Mac expert Dr. Howard Oakley told Lifewire via email.

"Although this is often stated as being for better security, there's a much bigger reason for these changes which should be an improvement for every Mac user: updates and system integrity should now be almost totally reliable.”  

Big Changes

According to Oakley’s numbers, macOS Mojave totaled just 21.5 GB of updates during its year as the newest Mac operating system. Three versions later, Big Sur has just topped 50 GB.

I’m...confident that they will significantly reduce that overhead. But I don't think we'll ever see updates of less than 500 MB.

Part of this is down to Apple’s new M1 Macs. Now, every update has to run on both Intel and Apple Silicon Macs, which ups the size. And finally, those M1 updates are themselves bigger. On Big Sur, the minimum update size for Intel Macs is 2.2 GB. For M1 Macs, it’s 3.1 GB.

These huge updates waste all kinds of resources, but for most people, the one they’ll notice will be their wasted time.

"The biggest downside of these large updates is probably the time it takes to download and the memory space it can take up on an older computer," tech enthusiast, Mac user and technology writer JP Zhang told Lifewire via email. "With updates often taking anywhere from 30-60 minutes, you will have a noticeable amount of downtime."

Why So Big?

There seems to be no need for such huge updates, especially as the actual software payload delivered is much smaller than the download size. Part of the problem is Apple’s security model, which only lets you download authenticated updates direct from Apple. Every Mac gets the same update, which means it has to contain data for all Macs that may receive it.

But the advantages of Apple’s new approach are clear. Never again (in theory at least) will a software update leave your Mac dead or unresponsive. 

A person using a MacBook computer at a meeting.

Christina@wocintechchat.com / Unsplash

"We got used to some macOS updates leaving our Macs almost unusable, to having to keep reinstalling macOS because something in it had apparently become corrupted," says Oakley. "The sealed system volume in Big Sur should make those problems a thing of the past."

In this way, it’s a lot more like iOS, which we update without ever worrying about problems. Apple seems to have gotten that part down, so now it’s time to see about shrinking these updates.

"What those engineers need to turn their attention to next, during Monterey's cycle, is reducing the overhead in its updates," says Oakley. "I’m sure this is where they're going next, and confident that they will significantly reduce that overhead. But I don't think we'll ever see updates of less than 500 MB."


If you have a Mac with limited spare storage space or a slow or capped internet connection, what can you do in the meantime to avoid those big downloads?

Not much. You could skip intermediate updates, but as these are often essential security fixes, that may not be a good idea. Another option is to use the Mac’s Content Caching Server, a built-in feature that keeps a cache of software updates. Other computers on the same network can grab the contents of this cache instead of downloading it fresh. This can mean zero extra downloading for Macs with matching chips (all Intel, for example) and small, ~1 GB extras for M1 Macs. 

A mac computer with an iMac behind it going through an update.

Muhammed Abiodun / Unsplash

Another option is to set your Mac to download updates in the background and alert you when they’re ready. This takes away the waiting part. 

But like everything else in tech, software and files tend to bloat to fill the available resources, and software updates are no exception. Maybe macOS Monterey, arriving this fall, will shrink its updates, but the general trend is toward bigger updates. We’ll just have to get used to it.

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