Apple Silicon Mac users may be in for much bigger system update downloads than they expect or than the software updater says.

Howard Oakley, of The Electric Light Company, compared system update downloads for Apple’s Intel Macs and its Silicon Macs. There was a significant discrepancy between the two in terms of the download size of the updates.

Way back in the first updates for M1 Macs in Big Sur, it became clear that updates provided to those models consisted of two distinct components or phases in the update process. The first download was similar in size to that for Intel Macs, and essentially the size given for the update by software update. In the case of the 13.5.1 update, that was around 500 MB for Intel, and just over 700 MB for Apple silicon Macs. As that part of each update should be similar between different architectures, there’s usually little difference. However, there’s a second component that is only downloaded by Apple silicon Macs, which is generally about 1.1 GB in size, bringing the total size to be downloaded to about 1.8 GB.

The revelation could have a significant impact on users that have slower or metered internet access. Apple should update its notifications to accurately reflect the true download size of updates on its Silicon Macs.