Now that Monterey has moved to security updates only, it’s time to take stock of its updates. If you survived the full Big Sur cycle, you’ll remember its huge updates, made all the more ironic by Apple’s claimed feature of macOS 11 making it “easier than ever to keep your Mac up to date and secure.”

The headline for Monterey is that, over its year as the current version of macOS, it only required around 22-26 GB of macOS updates; that’s less than Catalina, and only slightly more than Mojave.

Among the factors determining the total size of updates during a cycle are:

• number of bugs to be fixed, and the size of patches required;
• overhead in each update, including bundled firmware updates;
• number of updates required;
• updates became Universal binaries from 11.0 onwards;
• additional overhead apparently required by Apple silicon Macs.

Big Sur fared badly in several of those, as it was the first version of macOS to use Apple’s new installer/updater system designed to work with its new Signed System Volume (SSV). It was also the first cycle in which macOS and its updates have been Universal binaries, which roughly doubles the size of executable code to be delivered in each update. Apple didn’t name it Big Sur for nothing.

Monterey also required fewer urgent patches in between its scheduled updates. Whereas we had become accustomed to multiple quick fixes, even the odd Supplemental Update 2, in previous versions, there were only three patches, for 12.2.1, 12.3.1, and 12.5.1. That suggests Monterey had fewer major gaffes and security flaws, which is encouraging. Hopefully Ventura’s Rapid Security Responses (RSRs) will reduce those further.

Monterey’s largest update was 12.3, which weighed in at around 5 GB and was released in mid-March, probably carrying the brunt of the fixes in response to its early releases. That also brought the first working version of Universal Control, although even then it was still officially a beta, and other features including Visual Look Up and Spatial Audio. Although we didn’t know at the time, it brought the first release of Apple’s new anti-malware scanners, XProtect Remediator. Looking back, the x.3 update has become the most important after the initial release, in terms of new features.

Apple appears to have tweaked the architecture of Monterey to enable smaller updates. Big Sur’s smallest was 2.2 GB for Intel models, and 3.1 GB for M1 Macs. Monterey 12.1 weighed in at a mere 1 GB (Intel) and 1.9 GB (Apple silicon), around half the size. This shows a marked reduction in the overhead which isn’t attributable to omission of firmware updates, for instance.

It appears related to the increasing use of cryptographically-sealed extensions, or cryptexes, to extend the existing SSV. In other words, Apple’s engineers are increasing the efficiency of updates by moving selected system components from the SSV, where they had to be replaced during an update, to cryptexes, where they can be patched instead.

Finer detail is shown in the graphical comparison between cumulative update sizes during the first year after release for macOS from Mojave to Monterey, below.

Mojave, the last conventional macOS which installed into a single combined volume and had no support for Apple silicon, is unsurprisingly seen in the blue line at the bottom. Catalina, with its boot volume group but still single-architecture, is the purple line above that. The top two black lines show Big Sur hanging its head in shame, and Monterey is the much more spritely pair of red lines, ending up between Mojave and Catalina.

I’m impressed, and thank Apple’s engineers for responding so effectively to our whining when we had to install yet another huge Big Sur update. Maybe Marketing would have better making the promise of “easier than ever” updates for Monterey, rather than Big Big Sur.