Big Sur 11.5 Download Failed

If this update is for Big Sur 11.5 - the error message can be misleading. There are factors like poor Wifi connection, slow wifi connection, too many other people downloading at the same time and Apple Severs are overloaded, Software on the computer interfering with the download process, running behind a VPN and or / if via wifi too many Other devices using the wifi at the same time reducing the Bandwidth to you computer.

Best Results are via Ethernet Cable to Router

There are several ways to download the Big Sur 11.5 update. 

1 - Connect to Router via Ethernet connection and restart the computer in Safe Mode and then open the Apple Apps Store and get the Full Installer of Big Sur. It will be the 11.5 version and once downloaded run the installer from the Applications folder.

2 - Resart the computer in Recovery Mode ( INTEL Command + r ) and choose Reinstall macOS. It too will download the full Installer and commence the installation. For M1 CPU the Recovery Mode is Here

3 - This method may seem unnecessary but sometimes the Router Restart clears Network issues from ISP to Apple Servers

Shutdown Router. Shutdown computer and disconnect all External Drives. Restart Router. Connect to Router via Ethernet Cable. If via Wifi - Disconnect all other Devices using the Wifi - want the Maximum Bandwidth only for this computer. Restart computer in  Safe Mode. It does a Repair Disk, Clear System Cache files and only load Apple Software, extensions and Fonts. Will load slowly - Normal. Once Logged in - open Apple Apps Store and  Get the Full Version of Big Sur. It will take some time and several pauses will occur - normal. Countdown clock may say 15 minutes but in Real time may be 30 minutes. Same goes for clock at 10 minutes could be 20 minutes in Real time. Eventually , Full Installer will download and a New Application in Applications Folder will present called Install Big Sur. Stop there and perform a Time Machine Backup. If desired - have an External Drive - Copy & Paste the Install Big Sur Application to external drive for future usage - making a Bootable Installer. Now run the Installer.

Have found this method more reliable than the Software Update which is very iffy at best

Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation. They may also interfere with the Download process

There is indeed a way to fix this issue. I have experienced the same, but was able to finally successfully download Big Sur 11.5.1 using the following steps:

• Go to the Terminal and run

softwareupdate -i -a --force

• Wait for the download to be completed, then head over Software Update under System Preferences to restart your mac

That should fix the bug, and I have tried this with success on both my intel and M1 laptops.

Hands down the most frustrating Apple system update experience ever.

Apple Support thread : How to upgrade to macOS Big Sur - Apple Support , states "If upgrading from macOS Sierra or later, your Mac needs 35.5GB of available storage to upgrade..." The system which experienced this Big Sur 10.5.1 Update error is an Intel 2018 MBP 4 TB Ports with more than the required amount specified by the above Apple Support thread. I was unsuccessful via the terminal softwareupdate command method. The method that ended up working for me was creating a bootable USB Mac OS installer of the Mac OS Big Sur 10.5.1 update. This Apple Support thread will explain the process to create install media : How to create a bootable installer for macOS - Apple Support.

Steps taken to achieve successful installation of Big Sur 10.5.1 Update:

1. Download Big Sur directly from App Store, not from About this Mac > Software Update.
2. Create USB bootable installer for macOS using the Big Sur installer downloaded in step 1.
3. With bootable install media plugged into your mac shutdown or restart Mac, on Mac startup hold down the option key , when option for startup disc appears on screen choose the install media.
4. Follow any on screen prompts that appear through completion of Big Sur Installer program.

I experienced the same issue (error message downloading the update) but it was not related to network or internet connection. It was simply lack of disk space. So after cleaning up a bit - freed approx 18 gb - I was able to download and install.

Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation.They may also interfere with the Download process

it does not work whatever the connexion. The result is the same when trying to install the update via the terminal except it seems to indicate there not enough available free space to install ( what seems to be wrong as the normal update process let know the necessary free space to get when required ).

I experienced the same issue (error message downloading the update) but it was not related to network or internet connection. It was simply lack of disk space. So after cleaning up a bit - freed approx 18 gb - I was able to download and install.

Like ( but not the same) Apple stated for the upgrade from Previous versions of macOS - there are Empty Space Requirements. Updates will require Empty Space to download, expand and install.

Good and Responsible Apple Computer Management is a prerequisite for the update to download and install successfully. There should Always be at least 15 % of the internal Drive as Empty Space at all times for the computer to function properly. In this case - one may have let the drive to become too full. Caution - if this is correct and not attended to properly and soon - the computer may give a warning of " Computer is running out of Space " if that occurs, and left unattended to - the computer may eventually stop Booting at ALL.

This might or might not be relevant: I was having problem downloading and installing macOS Big Sur 11.5.1. The GUI (Software Update) was failing with "Internet Problem". The "softwareupdate" tool from the terminal gave more useful error message "An additional 1.92 GB of space is needed". After freeing up some space restarting the softwareupdate started the download (still waiting for the update to finish):

Following is the output from my terminal:

% softwareupdate -l
Software Update Tool

Finding available software
Software Update found the following new or updated software:
* Label: macOS Big Sur 11.5.1-20G80
	Title: macOS Big Sur 11.5.1, Version: 11.5.1, Size: 2859335K, Recommended: YES, Action: restart,

% softwareupdate -i 'macOS Big Sur 11.5.1-20G80'
Software Update Tool

Finding available software
Downloading macOS Big Sur 11.5.1
Downloading: 100.00%
Failed to download & prepare update: Error Domain=SUMacControllerError Code=7722 "[SUMacControllerErrorPreflightPrerequisiteCheckFailed=7722] Failed to perform PreflightPrerequisite operation: com.apple.BuildInfo.preflight.error(Preflight):BIPreflightErrorTargetOutOfSpace(16) | The target volume does not have enough free space to install.
An additional 1.92 GB of space is needed to install on this disk.


% softwareupdate -i 'macOS Big Sur 11.5.1-20G80'
Software Update Tool

Finding available software
Downloading macOS Big Sur 11.5.1
Downloading: 68.47%

In case it still doesn't work remember to also try the "--force" tag. I tried it without this tag before but was "told" by the error log that there was some internet connection error. Hence this tag might indeed be very important in fixing this bug.

In my case I did not need to provide "--force" tag, but the download did took some time to finish (using Ethernet cable, connected to a corporate network).

`softwareupdate --history` executed in the terminal now shows I am running macOS Big Sur 11.5.1, and there are no updates pending.

Concludion: Software Update GUI tool incorrectly reports "out of disk space" error as "internet problems".

I am also facing same error after downloading big sur 11.5.1 almost 3.4 gb. Seems issue is in big sur package.

Because I tried multiple times and lost around 20 gb data and always failed. I don’t see any internet connection issue.

Thanks,

Amul Patel

YAY! I skipped the big long network one and tried your solution first because it seemed MUCH more likely. I had 13GB of space free, freed up 4GB and it updated just fine! So, I'd recommend others START here! Then try the long network related one.

I have tried 13 times to do this update in my iMac....which worked like a charm the first time on my MBP....and it downloads the 2.93GB and says it is preparing the update. Then, sometimes immediately, sometimes after the progress bar has made some progress, I get the message "Download Failed."

I have plenty of HD space... over 990 GB, so the problem isn't there. The internet is functioning fine and is the same one I used for the MBP, so I doubt that's the issue.

I had the same problem, I tried to update several times, but had the same problem everytime time.

Finally, after closing the anti-virus program "Kaspersky Internet Security" the update 11.5.1 was sucessfully installed.