I have the same issue here :(

Mine seems to have resolved, but no idea how.

One theory I had was that I actually needed space for the full install instead of just the update. So if you have a 30gb game with 5gb update you would need 30gb of free space instead of just the 5gb.

I think you are right with your theory. My disk space wasn't
particularly high at the time!

One thing I noticed that it is often not clear how much disk space is needed for an update, as it can consist of several files from small to huge but it will already stop at a small file. E.g. the update may be 10gb big in total but split into a 2 mb File and one of 9998 mb. However the client may then only show you to refuse the download of a 2 MB file combined with the confusing message mentioned above.

I see this when trying to install 5 GB update on a HDD having 120 GB free. it's arch linux, no quota enabled.

I just reproduced the issue while trying to re-install "ARK: Survival Evolved" on an empty 3TB HDD. (the steamapps/common folder is on this drive). I don't use quota.
The game package to download is about 43 GB.
The game itself needs about 130 GB of disk when installed.

My steamapps/downloading folder is symlinked on a smaller SSD drive with only 100 GB free space.

So for my case: it seems that Steam clients ~erroneously~ checks for 130GB free space on the drive that holds steamapps/downloading folder, instead of checking the drive that holds the destination folder ( steampapps/common ).

If I remove the symlink and let the download happen on the empty 3TB drive, the problem disappear.

Edit : it seems Steam client really needs 130GB free space in the steamapps/downloading folder, as it uncompress data "on the fly" ?

seconded

sudo mv ~/.local/share/Steam /second-disk somehow solved it for me, don't know why but it downloads normally now

I was getting this error today when trying to download a 13.4GB update for Stalker 2 on a disk with 90GB free space. It seems that the 13.4GB is misleading and the update actually wants 141GB which can be seen when hovering the mouse over the error message (which is also misleading since most of us don't use quotas on our home PC :) ).

After reading the comments above and symlinking my steamapps/downloading directory to one on a bigger disk the problem seems to be fixed.

Thanks @af7567 for noticing the mouse hover number!!

The upgrade requires the amount indicated when you hover the mouse over the error message.

The symlink trick is a great trick if you can't free up enough space on the current drive.

My experience ( the long story):

• Misleadingly stated it needed 4.1GB for upgrade, hover over error said 40GB.
• I freed up 60GB and was able to do the update:
• It filled up the steam/steamapps/downloading/### dir with 37.7GB ( only 4.1GB of which was from downloading, the rest I assume was copied from the existing install)
• When it finished the above download dir went to 0 and the steam/steamapps/common/NameOfGame increased in size by 2.8GB (from 82.4 to 85.2GB).
• The overall /home/me dir got up to aprox 779GB and back down to 744.1GB after the upgrade. This checked with the numbers earlier ( 34.9GB + 2.8GB = 37.7GB ).

So in summary. It required 37.7GB of temporary downloading space resulting in an additional 2.8GB of game install space.

this is still a bug, right? my SSD is pretty small, I have Overwatch to update (Steam says 4.1GB but when hovering into the error I see 53.29GB), but I don't have this much space and I definitely have required files, so I'm forced to reinstall the whole game because of it.

Weirdly enough I also found this thread after trying to update Overwatch, it might be a game-specific issue because I had over 150GB of free storage and Steam was convinced I don't have enough space to update it...