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What’s Behind Mysterious Cellular Data Usage in iOS 6?

My Twitter feed is full of people telling me about mysterious data usage over cellular networks after installing iOS 6 or acquiring an iPhone 5. Adam Engst already penned an article explaining potential causes and solutions for fast battery draining in iOS 6 (see “Solving iOS 6 Battery Drain Problems,” 28 September 2012). This may have some bearing on the unexpected cell data consumption, too, especially given that he tracked his problems to corrupted Safari bookmarks syncing constantly through iCloud, which could happen while away from a Wi-Fi network.

But many of the reports I’ve received are from people whose iPhones are set to use Wi-Fi, and the phones show a Wi-Fi network connection item when woken from sleep. One Twitter buddy, Anthony Hecht, says AT&T told him that when his iPhone is in “idle mode” (standby), it always reverts to cellular, which is wrong. AT&T customer service also told him to turn cellular data off (Settings > General > Cellular Data) whenever it’s idle, which is crazy making. He has seen 9 GB in unexpected mobile use, largely while at home based on his online charge breakdown, in just a week.

Many people attributed this problem to usage by Apple’s Podcasts app, which has been documented to exhibit bad behavior when downloading and streaming over cellular (see “Does Apple’s Podcasts App Suck Cellular Data?,” 17 September 2012). It can download the same podcast file repeatedly. Even after Apple added a switch in Podcasts 1.1 to restrict data use to Wi-Fi, my colleagues can still track cellular downloads with the app, especially if a download or streaming was already in progress when walking away from a Wi-Fi connection.

But several people have also eliminated Podcasts and other podcasting apps as culprits. They can see from their online data usage and from iOS’s tracking of cellular data (or by using DataMan) that the device chews through hundreds of megabytes of cell data over short periods of time, and they don’t know why. Josh Centers is in the middle of a quest to figure this out, and I expect others are as well.

John Herbert seems to have found one particular bad use case when iTunes Match will download over a mobile broadband network even when all the switches to use cellular data with Music and iTunes Match are flipped to Off. His entry on the topic explains how these settings are currently ignored when you start to download items from the cloud or have music downloads in queue.

Verizon has released a “carrier settings update”, which is supposed to deal with technical issues of connecting an iPhone to a given mobile network, and it apparently has to do with an iPhone 5 using the cellular data network instead of Wi-Fi even when connected to a Wi-Fi network. This doesn’t explain AT&T users’ problems nor those of people with earlier iPhone models experiencing the same data consumption.

Over at the Economist’s Babbage blog, I suggested that it’s hard to pin down blame when one can’t currently measure per-app use and thus figure out what’s going on. That was possible with DataMan Pro, which Adam Engst started testing for review before Apple pulled it from the App Store, but for most people trying to figure out what’s happening is completely frustrating — and expensive! This isn’t “CellularDataGate,” but it’s clearly affecting more than just a handful of people, and could involve folks paying tens or even hundreds of dollars in excess data usage because of what might be a bug in iOS 6 or Apple-provided apps.


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Comments about What’s Behind Mysterious Cellular Data Usage in iOS 6?
(Comments are closed.)

Abhimat  2012-09-29 13:51
It’s been driving me crazy trying to figure out what could be causing the huge data drain on my iPhone 4 on iOS 6. As best as I have been able to figure it, it seems to be due to the Podcasts app.
Peter Rustin  2012-09-29 15:59
I used 499 mb in 3 days with a vz 1phone 5; my ATT 4s used 1 gig /mo. It accesses cell while over wifi AND uses weirdly high data (250mb to download a single 63 mb podcast). This IS cellular gate and when the overage bills come out there will be a HUGE uproar
William Lisowski  2012-09-29 18:58
I have confirmed that by pressing a link in Safari and choosing Add to Reading List from the pop up menu, it is possible to inadvertently chew through one's data plan by downloading a video for viewing later, thanks to the new (mis)behavior of Reading List. Had I opened the page, the video would not have downloaded until I clicked on it, but that subtlety was overlooked by Safari.

Kudos to the invaluable app Data Usage for helping me track this down. Brickbats to Apple for this change in expected behavior with no way to reverse it.
William Lisowski  2012-10-03 09:28
Amending my previous post, the problem lies not in Reading List but in WebKit. From both Safari and my RSS reader, I have opened web pages containing linked video (e.g. a cruise line ad on a page on the NYT, a video link on the TPM RSS feed) only to find a 20-50MB or more of cellular usage since immediately before opening the page. This did not happen on iOS5 and it is not limited to a single web site, but it also does not seem to happen consistently. I'm using a third-generation iPad on Verizon LTE.
William Lisowski  2013-01-29 17:55
It appears that the iOS 6.1 update addresses at least the problem I encountered on my iPad.

I did a before-and-after test of the URL given below, surrounding my update to iOS 6.1 from 6.0.1. Before, I see a video near the top on the right side of the page, just below the banner ad, briefly showing the "play" button, but then downloading and playing on its own. After installing iOS 6.1, the video no longer began playing on its own. Subsequent testing confirms that the video had not been quietly downloaded, either.
artMonster  2012-09-29 21:18
Saw this link:
Commenter wonders, "Perhaps they’ve just removed the option from the UI and made this behavior the norm?"
Let's hope not.
Josh Centers  2012-09-29 23:57
Thanks for the link, Glenn! So far, wiping and starting fresh has seemed to restore my data usage to normal.

A question for anyone who's seen a data usage spike since switching to the iPhone 5: Did you switch carriers and/or restore from a backup?
Adam Engst  An apple icon for a TidBITS Staffer 2012-09-30 16:27
I set my iPhone 5 up as a new iPhone to resolve the battery drain issue in iOS 6, and I've still seen bad behavior. Just this morning, for instance, I was at home on Wi-Fi. I set some podcasts to start downloading in the Podcasts app, so they would definitely be on the iPhone when I left for a car trip. Shortly thereafter, while doing something else, I discovered that my Internet connection was having trouble, so I reset the cable modem. It was probably down for about 5 minutes, max. In that time, DataMan Pro alerted me instantly to tell me that something had downloaded 31 MB of data via cellular, even though I have all Podcasts and iTunes switches set to Wi-Fi only. Unfortunately, because I'd set up the iPhone 5 from scratch, I'd lost the DataMan setting where it tracks by app, so I couldn't see what app was responsible. I strongly suspect Podcasts and related processes, though.
Michael F.  2012-09-30 00:22
Two things:

1) There is a new data monitoring app that is *very* impressive, out of Princeton University - it gives much better and more useful info than Dataman did, at least when I last used Dataman. It's called Datawiz, and it's free on the App Store. It can tell you where and when you are using 3G and Wifi data, and alert you when you reach certain fractions of your data cap, including daily and weekly prorated targets.

2) As noted in Josh Centers' article, I ran into a battery + data drain article when upgrading my 4S to iOS6 as the result of a fairly nasty iCloud sync bug involving a corrupted Safari bookmarks file. The "webbookmarksd" process on the phone would crash and loop repeatedly. The tricky part was figuring out that once the bookmark file had been "asked" to sync once with iCloud by running Safari with iCloud Safari Sync turned on, the bookmark file itself was now marked "sync me." (I confirmed this by extracting my bookmarks.db file from an iTunes backup and looking at it with a sqlite3 database tool.)

Turning iCloud syncing off didn't do anything - just launching Safari after that point would set off an eternal cycle of attempt to sync/crash/try again/etc, burning battery and data pretty fast. Restarting the phone was the only way to get it to stop, and that worked only until I launched Safari again, when the whole process would repeat.

The ugly details are at, along with the workaround that fixed it for me.

Adam Engst  An apple icon for a TidBITS Staffer 2012-09-30 16:29
I've downloaded DataWiz too, and it's graphically very impressive but doesn't have the app-specific reporting that the version of DataMan Pro I have (before Apple pulled it from the App Store) does. The basic version of DataMan is no more capable than DataWiz, unfortunately. I wish Apple would allow it back into the App Store.

Your battery drain sounds a lot like the one I tracked down too.
maxmost  2012-10-01 19:07
Due to a misdesign in Music App it is possible to download big amount of music data in 3G network also if your configuration "use cellular data" is switch off.
Charles Reeves Jr  2012-10-02 06:58
My experience has been just the opposite on my iPhone4. iOS6 fixed the battery drain problem I had been having ever since one of the iOS5 upgrades. It would be down to about 40% every morning; now it is above 80%. The excessive drainage had something to do with being within reach of my WiFi network; e.g., it didn't happen when visiting my son and his network.
Superbogey  2012-10-03 16:18
No problems - so far. iPhone 4S running iOS6 on Verizon shows only 4.9MB sent & 18.4MB received since resetting on the 20th (billing cycle) and I'm probably a medium web user & of apps needing access to it while on WiFi or Cellular.
My phone sucked over 3 gig of 3g data in one day on a 4s after playing with the podcast app on the day it started....I normaly use around 100-200mb per month
kauffee  2012-10-04 11:51
Noticing the same things as above... streaming from the podcast app causes outrageous data usage. Despite the total podcast being about 40mg, streaming it as i drove around town (so stopping and starting) caused about 350mb of data use (minus the few kb for intermittent email checks.)

Like Colin above, I also thought I noticed a big jump in data use with turn-by-turn directions but I wasn't sure.

Needless to say, this is pretty unsustainable.
douglas  2012-10-04 14:12
I all of the sudden started to experience rapid data usage on Verizon, with over 1 GB of data getting downloaded this morning. I suspect it's the podcast app trying to download the season premiere of Homeland (which I downloaded using the podcast app on my iPad). However, I've set my iphone not to download over cellular. My hunch is that my iPhone Podcast app (synced with my iPad Podcast App) began downloading Homeland while I was on wi-fi, and when I left home it kept downloading on cellular. I deleted the Podcast app and the data usage has stopped. Of course now i'm way over my data usage allotment on Verizon and I have no podcasts. :(
j robinson  2012-10-04 22:43
same as most on orange network unknown data usage i think its time apple did a roll back till they sort this mess out
Just had 1788 MB data usage in 4 hours - I average less than 100MB per day for the past 3 years - so yes there is an issue. I noticed the Podcasts app was super buggy this morning and then I got a txt from my provider saying I was over my usage. Apple needs to address this ASAP.
Anton Rang  2012-10-06 14:34
iOS 6 does measure per-application data usage, neatly sorting it into cellular and wi-fi buckets. It's found in a file called log-aggregated, which is created daily.

If you back up to your Mac using iTunes, you can find it in ~/Library/Logs/CrashReporter/MobileDevice. You can also view it on your iPhone under Settings/General/About/Diagnostics & Usage.

In this file, towards the end, you'll see entries that look something like


These two entries tell me that the AP News app downloaded about 3.8 MB on WiFi, and that Mail downloaded about 66 KB via cellular, for that day. There are similar entries for uploaded data and for the UDP protocol.

(I seem to recall seeing these with iOS 5 as well, but no longer have a device to check.)
Adam Engst  An apple icon for a TidBITS Staffer 2012-10-06 17:33
I imagine this is the data that DataMan Pro was analyzing, and which Apple didn't want them accessing.
Joseph McIntyre  2012-10-08 10:24
Interestingly, on my iPhone 4S and on my computer, I am not finding this data. In General Settings as you describe, it says no diagnostic data and on my Mac there are no log files as you describe. I have had the option to send diagnostic info to Apple off. I wonder if this is preventing capture of this log data?
walueg  2012-10-12 11:36
I'm not only getting higher than normal data, but on public wi-fi networks, I have to restart my devices everytime I change access points, even within a network. It's at these public networks that I am also getting the most battery drain. I turned off cellular data this morning and it's back to normal.
Matt Smith  2012-10-15 09:56
My iPhone 4 managed to download 8.1 GB's overnight. Carrier has charged me over $1000 (South Africa)in excess data usage and refuses to budge. Told me to complain to Apple
Adam Engst  An apple icon for a TidBITS Staffer 2012-10-15 10:13
Ouch! That's the one of the worst cases I've heard yet. We've been trying hard to track this down, but we haven't found any smoking guns yet, despite some of us having seen the excessive data usage ourselves at times.
Sad iphone guy  2012-10-16 14:57
Checking the Usage on dataman app, iphone 5 on att is using 10kb per second.
i'm fairly certain it is the podcast app in my case. i just got a message that i've used half of my data for the month and i have only had my iphone 5 for a week. i have it set to only use wi-fi, but the unplayed episodes list will still show undownloaded episodes and yesterday i noticed it was playing through items that i didn't believe were downloaded.
Adam Engst  An apple icon for a TidBITS Staffer 2012-10-18 12:26
Yes, the Podcats app will definitiely move from playing a downloaded podcast to one that needs to be streamed with no warning or control. The Use Cellular Data option applies ONLY to Auto Download, not to streaming in general.
ok. now i look at the verizon site and apparently i used 1.3gb last night while i was home on wi-fi! i have that system update to fix that.
Todd Stancil  2012-10-19 04:05
I have podcast app not syncing or downloading or anything. Everything else is off. I'm still getting data being sent at between 80mb and 500mb at a time. Most while I'm even connected to wifi. For the past 3.5 years, I"ve never gone over 200mb data per month. Now in 18 days, I've hit 3g and it's all been data that's been sent from my phone.
ItsNotTheSameWithoutSteve  2012-10-24 20:47
Verizon's fixed this already, that's why you Verizon users have no problems. My phone, using Dataman logs 139K per minute, INSANE! I've done EVERYTHING, shut everything off, and even restored it through iTunes. Still sucking down data like mad. APPLE FIX THIS NOW!!!!!
Thanks for your effort to write this article.

Short answer from my side:


ca. 30MByte per hour up/download

iPhone usage and standby: nearly the same numbers

Battery life: 2-2.5h "standby". Backside of the iPhone was warm.

Apple Genius Bar: it is the provider

Provider: it is Apple

From my perspective: neither apple nor the provider

After a deep investigation (and your article) I found 2 root-causes:

1) Safari bookmarks: the plist file has had a size of 3,5MB (uncountable of bookmarks, and furthermore very very old bookmarks)

2) My companies Exchange account.


1) Bookmarks: I have deleted the old bookmarks, exported the rest of the bookmarks, reset of Safari, import the bookmarks.

2) Deleted the account: no result. deleted all e-mails accounts (Exchange, iCloud and a second private account)


After that all everything was fine.
Adam Engst  An apple icon for a TidBITS Staffer 2012-10-27 11:20
This sounds a lot like my battery drain issue.
Uh, I'm on AT&T and that's a problem since it's a crappy network. But battery life? I'll just get a different type of phone. The iPhone that I have (a 3GS) is the LOUSIEST cellphone I've ever owned and it's not even worth the $0 I paid AT&T for it. They should have paid me to try to use it.

I will not get another Apple phone regardless of what it is or isn't. They're late to the party and who really cares if it's a 3 or a 4 or a 5. It's just not worth it. They just want our money. Oh, and they will come out with a 6. You can bet on it....
Tom Lusch  2012-11-13 23:04
Wife & I have been on AT&T'S 250MB/mo ($15/mo) plan since day one (Mar 2011 & Dec 2010 respectively), and we have _never_ exceeded 250MB limit. Right near beginning of this data period (Oct 21 thru Nov 20) got message indicating wife's iPhone 4S nearing limit, then today (Nov 13) her plan went over. site showed three instances of VERY LARGE DATA USAGE (44.5MB on 10/20, 62.2 MB on 10/26, and then 119.5MB on 11/12). Cannot correlate any big file transfers at the 3 date/times indicated. Dumbfounded as to what took place, as wife was home each time, where we have wi-fi.

Note that _during this period_ updated wife's 4S to iOS6 (on 10/31), so first two suspicious large data usages are _not_ related to having the updated OS. (Thus far my iPhone 4 usage typical. I updated it to iOS6 on 11/8.)

On phone for nearly 2 hours tonight, being bounced around between AppleCare & ATT, but they offered no truly helpful technical assistance.

Tom Lusch  2012-11-14 11:44
On above, I incorrectly stated 250MB plan. I should've said 200MB plan. After posting above, I did come across "Dataman Pro" (see, and downloaded. It specifically states "Now you can root out data-hungry apps...". After than, I decided to do the dishes before retiring. While doing dishes, I got caught up on some news by selecting stories on Fox News app, and listened to them (had iPhone in pocket). Then I headed for bed, but noticed Dataman Pro was advising of high cellular data usage. It appears that my "listening" to the news while washing dishes resulted in nearly 70MB of cellular data usage within 20 minutes! This was on my iPhone 4 (not wife's 4S). When I viewed Dataman Pro's application ranking, it showed "Media Server" (Quicktime icon) as highest usage. Since I had iPhone in pocket during this period, I don't know if wi-fi dropped out during this nearly 20 minute period or what. But something is fishy that resulted in high cellular usage.
Adam Engst  An apple icon for a TidBITS Staffer 2012-11-14 13:08
The current version of DataMan Pro can't yet show per-app usage levels, but they're trying to get that feature past Apple again. I don't believe the list of apps the current version shows is necessarily in order of usage, either. But it's at least giving you some indication of what's going on.
William Lisowski  2012-11-14 15:21
According to a version of DataMan Pro was released on 13 November that restores per-app monitoring, with other benefits. I'm guessing that Tom was fortunate enough to run across it on its first day out, and that Adam's comment reflected the previous version. According to the website, it constitutes a "new app" since Apple removed the previous version, and has to be purchased again if you had the previous version. I'm guessing it won't badge your App Store icon, so you either have to hear about it from someone (thanks, Tom!) or be looking for it to have returned to the App Store.
Adam Engst  An apple icon for a TidBITS Staffer 2012-11-14 15:44
No, alas, I'm in touch with the DataMan Pro developer, and the current version does not have per-app stats. It does do some level of per-app monitoring, so it will tell you which apps were active during a particular time period, but it won't tell you how much cellular data each one used, or differentiate between cellular and Wi-Fi usage. The developer is working on getting that feature back into the app and past Apple (it is in the earlier version that Apple pulled from the App Store that I have). I've told the developer I can't recommend the app until it has that feature back, since it's just not that helpful as it stands now.
Tom Lusch  2012-11-15 17:49
You are absolutely correct about it not having per-app stats. Where I stated " highest usage", I made an assumption, and should have actually stated that the "Media Server"' app was at the top of the listing, whereas the "FoxNews" app was at the bottom of the listing.

In their FAQ they state "The list of apps is sorted in order of activity.", thus it *appears* that the lowest app is the most recent app active.

They go on to state "We're working on adding more statistics to this list, including the data used by each app, in the next free update." I sure look forward to that.

An interesting thing I've noted in the hourly stats, is that while I was asleep, there is activity showing BOTH as cellular data, and as wi-fi data. Thus, some app or apps are doing something in the background via the cellular network, even though wi-fi is available. It is much less usage than wi-fi, nevertheless it is consistent.
Tom Lusch  2012-11-15 21:17
Re stats, I just checked for correlation between what my Dataman app is telling me, and what my AT&T Usage Data Detail indicates. Using my 11/14 example, wherein I noted that Dataman indicated "nearly 70MB of cellular data usage within 20 minutes" it specifically showed 69.1 MB in the 02:00 to 03:00 (wee hour) time period. Yet, when I view my AT&T Data Detail, I see a 35826KB at 00:07 (just before I had installed Dataman), and the next entry is a text message at 12:01 that day (noon). Not a thing in between. As you may recall, I was extremely surprised to find that large cellular data usage from my playing some video news clips just before I finally hit the sack, as I was in my wi-fi area the entire time. Also, I see no record of those hourly tiny dribbles of cellular data that Dataman is reporting (i.e. 35.5KB, 28.7KB, 29.6KB, 30.3KB. at 03, 04, 05, 06).

I'm really left wondering why Dataman showed such a high cellular data usage (69.1MB), yet AT&T didn't bill me for that.
Melodie  2012-11-14 11:46
My husband and my shared data went from .50 gig to .75 gig in 8 hours. Our phones were dead and charging during part of that time. During the rest of that time we only used the waze app and a few minutes of facetime. We finally just turned the cellular data off. This happened two days after my husband updated to iOS6 and I updated during those 8 hours. It's ridiculous!!! Not happy right now!
Peter Lorraine  2012-11-16 22:59
My 4s / 6.0.1, wifes 4 / 6.0 both on AT&T, son's 4s / 6.0 on Virgin Canada. All are seeing increased data usage. My wife is on a 200 MB plan - for the last year she only cracked 100 MB once. After updating to ios 6 she used 300 MB on one day in October, and 150MB on Nov 12 when she was at home all day on wifi. She watched a few videos in Safari that day but should have been on wifi. She switched data off yesterday when she went through her limit - turned it on today for a few minutes to check her daughter's address and sucked up 20 MB in a few minutes before switching it off again. My son is at college in Toronto - he says a number of friends with iphones were hit with big data fees last month - he is on a pay-as-you-go-plan which blew out 2 days into the cycle. He's computer savvy and paranoid about data usage - if this isn't fixed he'll drop data entirely or switch back to an old Nexus S.