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Documents & Sync High Data Use Despite Turning Off iCloud Sync & Using Low Data Mode

iPhone 8 Plus, iOS 13.2.3

I first uncovered this issue two weeks ago when I was notified that I'd used 90% of my data for the month. Self-diagnosed iCloud sync issues as Documents & Sync had used up 5 GB of data in ~1 week. Here is what I did initially to troubleshoot the problem:


  1. Logged out, then back into iCloud, while on Wifi
  2. Turned on Low Data Mode
  3. Toggled iCloud Drive to "Off" under the Cellular menu
  4. Turned Photos to "Off" under the Cellular menu
  5. Turned off "Wifi Assist"
  6. Cleared my "Cellular Data" settings so I could more accurately track data usage


Since Sunday, 11/24, I've used 583 MB of data. Roughly half of that was through normal usage- Google Maps, ESPN Fantasy Football, Amazon, Twitter, Chrome. 280 MB was used by System Services with 234 MB of that for Documents & Sync. More specifically, between yesterday morning and this morning System Services has used 220 MB of data, almost entirely for Documents & Sync.


I am trying to figure out what is still causing the high data usage in Documents & Sync despite turning off the usual high users of cell data. During this period the only time I was not connected to Wifi was the 15 minute drive to my in-law's house for Thanksgiving or the 15 minute drive back to my home afterwards. Outside of that, the only other time I was not connected to Wifi was during a ~1 hour walk I took last night. I tracked the walk using the Workout app on my watch (Series 3, NO cellular) and I listened to a podcast I had already downloaded to the phone using Overcast. I believe workout tracking would have shown up under "Time & Location" and probably "Mapping," not "Documents & Sync." If the podcast had streamed for some reason, I would think it would have shown up under Overcast.


Outside of that, I'm kind of at a loss as to what could have caused this amount of data usage in a 24 hour period when I'm actively trying to slow data usage and spent most of that time on WiFi. Any ideas/suggestions? Thanks!


iPhone 8 Plus, iOS 12

Posted on Nov 29, 2019 7:25 AM

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Posted on Dec 6, 2019 10:09 AM

I found the same thread on Stack Exchange! After exhausting my troubleshooting ideas, I got in touch with Apple Support. They connected me to a Senior Engineer who remoted into my phone to help diagnose a fix. Ultimately what fixed it was logging out of iCloud, doing a hard reset of the phone while logged out, then logging back in to iCloud. I'd tried those things in different orders, but I had not tried a hard reset WHILE logged out of iCloud. Since logging back in on Wednesday night, my data usage has returned to normal. 3 total MB used over the last three days, CONSIDERABLY better than the 200-300 MB/day it was using. So if you're having this problem, I recommend trying this fix!

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Question marked as Best reply

Dec 6, 2019 10:09 AM in response to dyyuan

I found the same thread on Stack Exchange! After exhausting my troubleshooting ideas, I got in touch with Apple Support. They connected me to a Senior Engineer who remoted into my phone to help diagnose a fix. Ultimately what fixed it was logging out of iCloud, doing a hard reset of the phone while logged out, then logging back in to iCloud. I'd tried those things in different orders, but I had not tried a hard reset WHILE logged out of iCloud. Since logging back in on Wednesday night, my data usage has returned to normal. 3 total MB used over the last three days, CONSIDERABLY better than the 200-300 MB/day it was using. So if you're having this problem, I recommend trying this fix!

Dec 5, 2019 5:53 PM in response to carddante

had the same issue, Document and Sync takes up GB if I am out of wifi all day...

googled the answer non stop, tried all you did, even wiped the phone to start from scratch.

nothing helped...cell data still get used 200-300mb every time I leave the house for 15 min...

(low data mode helped to some extent but then I have to manually check all my emails etc)


I even had work setup a VPN to do always tunnel so we can see where the traffic goes...


Finally I ran into an article on stack exchange (by Alberto White) mentioning the same issue and he figured out it was iMessage. So I started to delete all the images / videos on iMessage, starting with 2 ppl I chat with the most.

(there seems to be no "select all" to delete pics and videos, so I deleted 15 at a time...what a pain).

I also set my iMessage to keep for 1 year only instead of forever...

Two days later, my Document and Sync usage is only at 8.1mb!


I guess there are some bugs within iMessage that keep on wanting to sync over cell instead of wifi...

Hope this helps...it's been driving me crazy for 2 months!

Documents & Sync High Data Use Despite Turning Off iCloud Sync & Using Low Data Mode

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