each Steam game you have which uses Steam Cloud saves has a specific quota for storage, this quota varies quite a bit, but some games have quite a lot of quota:

• BeamNG.drive: 953.67 MiB
• Disco Elysium: 93.13 GiB
• Euro Truck Simulator 2: 93.13 GiB
• Severed Steel: 93.13 GiB
• Star Wars Jedi Knight: Jedi Academy: 9.31 GiB
• Valheim: 93.13 GiB

chances are you don't have more than a few dozen megabytes of saves in any of these… so what if you could use the rest for nearly-free, general cloud storage?

Steam Cloud Drive

huh turns out this is trivially easy to take advantage of, you can just put a file into the saves folder for a game and it'll sync it

anyway i now have several gigabytes of old photos backed up in disco elysium's saves folder. if i could be bothered i'd write a script to sum all the available space across all my games and write data to it, but it's almost 4am and valve would probably ban me for it anyway

I was curious this morning and did some data gathering:

• You can get Steam's full app list from the ISteamApps/GetAppList web API
• Further, using the steam Python library, you can request full product info, which includes the quota information
• Finally, written to disk, you end up with 437.4 MB of data about all Steam's apps

so what does this data tell us? (all values at the time of writing, obviously; this will change as games are added to the platform)

1. The absolute maximum Steam Cloud storage for a given user who owns every item on Steam (so, Valve employees and possibly some journalists with blanket access) is 191,986,735,934,656 bytes, or approximately 192 terabytes
2. The average Steam Cloud quota for all items on Steam is 6,961,085,421 bytes, or approximately 7 gigabytes
3. The average Steam Cloud quota for all items on Steam which don't have a quota of 0 (which may be a misconfiguration or mean more complex rules are in play) is 7,453,769,302 bytes, or approximately 7.5 gigabytes

I don't currently have a script to load data for owned games, so let's extrapolate using the averages, shall we?

I own 480 games on Steam, according to my community profile 😰, 480 times 7,453,769,302 bytes is 3,577,809,264,960 bytes, so roughly 3.5 terabytes

here's my code to retrieve all the product data, requires the result of the GetAppList request saved to data/applist.json and steam installed from pip:

#!/usr/bin/env python3

import json
from steam.client import SteamClient
import sys

def main() -> int:
	client = SteamClient()
	client.anonymous_login()

	with open('data/applist.json') as applist_file:
		json_appdata = json.loads(applist_file.read())

	appids = [app['appid'] for app in json_appdata['applist']['apps']]

	product_data = client.get_product_info(apps=appids, timeout=None)

	with open('data/product_info.json', 'w') as product_info_file:
		product_info = json.dumps(product_data)
		product_info_file.write(product_info)

if __name__ == '__main__':
	sys.exit(main())

and finally, I used these jq incantations to compute the values above:

cat data/product_info.json | jq "[.apps[].ufs.quota | select(. != null and . != \"\") | tonumber] | add"

cat data/product_info.json | jq "[.apps[].ufs.quota | select(. != null and . != \"\") | tonumber] | add / length"

cat data/product_info.json | jq "[.apps[].ufs.quota | select(. != null and . != \"\" and . != \"0\") | tonumber] | add / length"