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Apple’s iCloud Drive Slows Down a Device’s Download Speed by 10Mbps

Was tuning my home Wifi and noticed that some of my Apple devices (iPad, iPhone, MacBook Pro, iMac Pro) were not getting the same download speeds when testing via Speedtest. On a Mac with two user accounts, one account would consistently get about 10Mbps faster speed than another account. Initially thinking that there might be a user-level app that was running on log in, a launchdaemon or launchagent process, or a browser extension that was causing the slowdown in the affected account led to a process of turning everything off. But still, the slowdown didn’t go away.

As this was affecting not only Macs, but iPads and iPhones, I started looking deeper into what was similar with the accounts and devices that had the slow speed. It turned out to be Apple’s iCloud Drive feature. All the slow devices were logged into iCloud, and specifically, had the iCloud Drive feature turned on. When that is turned on, the download speed is slowed by about 10Mbps. It’s like it reserves this for it’s own use and is not available for other applications. And it’s not just in http web traffic, it’s at the device level as testing via Speedtest in a web browser or using the CLI test via Terminal yields the same reduction in speed.

You can do this simple test yourself. Just run Speedtest on any of the devices with iCloud Drive on, and then off.¬†If you have a 100Mbps connection I suppose it doesn’t matter much, but losing 10Mbps isn’t what I signed up for in using iCloud Drive. Needless to say I’ve¬†disabled iCloud Drive across all of them and reclaimed by DL speed, and will use one of the other cloud storage services like Dropbox or OneDrive that doesn’t silently take away my download speed.

Affected devices: Macs running 10.15.7 and 11.0.1; iOS and iPadOS 14.2