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Mysterious iOS 6 Cellular Data Usage: A Deeper Look

It’s becoming more and more difficult to ignore the numerous reports that iOS 6 on an iPhone or iPad can use far more cellular data than iOS 5 or earlier systems did. Anecdotal evidence is hardly to be trusted, even when it arrives in large quantity, but surely a massive thread such as this one on the Apple Support Communities cannot consist entirely of people who are mistaken or misapprehending the phenomena. Moreover, some of us here at TidBITS are convinced that we’ve experienced the problem in our own lives.

In this article, which picks up on some themes already broached by Glenn Fleishman in TidBITS (see “What’s Behind Mysterious Cellular Data Usage in iOS 6?,” 29 September 2012) and in a Macworld podcast, I’ll try to distinguish several strands of the issue. But first, let’s agree on just why the issue is an issue. We can all accept, I think, the following two axioms:

  • Axiom 1 First and foremost, it’s all about money. For my iPhone, I pay $15 for the grandfathered-in minimal 200 MB per month cell data plan from AT&T. The penalties for exceeding this monthly limit ($15 for each subsequent 200 MB) are severe as a proportion of my monthly bill, and the penalties for exceeding it by a lot are really severe. Users are aware of this, and are careful in consequence. For my iPhone to cost me money gratuitously, beyond whatever control I can achieve through such care, is wrong.

  • Axiom 2 The expectation is that when your device has a Wi-Fi connection, as when it is sitting in your living room and can see your home network, it will use virtually no cellular data; all the data you ask for, such as fetching your mail or viewing a Web page, should come over Wi-Fi. I say “virtually” because some phone activities, such as checking your voicemail by way of the Phone app’s interface rather than dialing your voicemail manually, do require a cellular connection — but they use only a tiny amount of data. This expectation is both reasonable, because if it is violated there is a danger that you can exceed your data cap (see Axiom 1), and deeply ingrained, because that is demonstrably just how iOS 5 and earlier systems behaved.

With that said, it is clear that some of us at TidBITS have recently experienced cellular data usage in excess of our expectations or intentions, and that some users (as shown in the Apple Discussions thread I cited above, as well as in reader comments on Glenn’s article) have experienced cellular data usage massively in excess of their expectations or intentions. So something is going on. I think we can distinguish four broad themes in the gusher of information and speculation about this problem. By concentrating separately on these four themes, I hope to focus your attention on what you can do to stem the flow of unwanted and costly cellular data on your own device, until such time as Apple provides a system-level fix.

How To Measure -- How do you know how much cellular data your device is using? In my opinion, a third-party app can’t tell you; it just doesn’t have access to the needed information. When I started seeing unusual cellular usage on my own device, I installed DataWiz; the interface is delightful, but the numbers proved to be sufficiently different from other forms of measurement that I eventually removed it. Similarly, Adam Engst swears by DataMan, but in the same breath adds all sort of caveats about making sure it’s running; DataMan Pro, which had the power to point the finger at individual processes using cell data, was removed from the App Store by Apple, although Adam and other early purchasers still have it.

In my view, there are only two numbers you should accept as meaningful. One is from the device itself, as reflected in the Settings app. Go to Settings > General > Usage > Cellular Usage. The numbers shown here are cumulative, so in order to know whether there’s been a sudden recent spike you may need to have made a note the last time you checked. But by deliberately pressing Reset Statistics on the first day of your monthly billing cycle, you can get a sense of whether you’re likely to exceed your cap this month. Of course, you have to know what day of the month that is, and it’s a pain to remember to do it; but the Calendar app can help you set a reminder that eases the pain.

The second important number — perhaps the only definitive one — is what your cellular provider says. After all, the real question is not how much data the iPhone thinks it’s using, but whether your provider is likely to charge you for exceeding your cap. You may be able to check your provider’s usage figures in an automated fashion. For example, on my iPhone, I go to Settings > Phone > AT&T Services, and am shown a number I can dial to View My Data and Msg (*3282#). Tapping that number causes a text message from AT&T to arrive in the Messages app, telling me when the next bill cycle starts and how much data I’ve used so far in this cycle.

Inspect Your Settings -- iOS 6 introduces a lot of new settings, squirreled away in various places, enabling you to specify explicitly whether an app should be allowed to use cellular data, or implicitly whether some process should be allowed to communicate over the network at all (the implication being, if it wants to communicate when you’re in the field, it will certainly use cellular if it can). It is worth taking some time to walk recursively through all your settings, looking for those controls. This is a boring and tedious operation, but hey, we’re talking about your money here. The difficulty is compounded by the fact that the implications of a setting may not be obvious.

Before listing some of these miscellaneous settings, I must say something about the master setting at Settings > General > Cellular. There is a master Cellular Data switch at the top here, and I’m certain that it does what it implies: if you switch it to OFF, the cell radio is effectively turned off, and although the phone still works for voice, you absolutely positively can’t use any cell data under any circumstances. You are unlikely to want to use this switch, though, since it hampers your use of the device. For example, you can’t check your voicemail easily. Plus, having this switch turned off caused Find My Friends to fail to track me when I was driving to pick up Adam in North Hollywood last week (and caused his text message to me to traverse the SMS system rather than Apple’s free iMessage system). On the other hand, why was it off? Because my phone is using excessive cell data, and switching this setting to OFF prevents that! So it’s Catch-22.

Here are some other settings to notice. Observe that I have no special information about what they really do or what effect they really have on cell data usage; I’m merely suggesting that they might be worth toggling in order to try to keep cell usage down:

  • Settings > General > About > Advertising: I’m told that the Limit Ad Tracking switch can affect cellular use, and that to minimize such use you want the switch ON (because this will limit ad tracking, don’t you see).

  • Settings > General > About > Diagnostics & Usage: Tap Don’t Send to prevent behind-the-scenes communication of diagnostic information back to Apple.

  • Settings > General > Cellular: Scroll down to see several Use Cellular Data For switches. Clearly if you don’t want these processes using cell data, you should switch them OFF.

  • Settings > General > Date & Time: Switch Set Automatically to OFF, perhaps, though one hardly suspects time queries of using much data.

  • Settings > Privacy > Location Services > System Services: Set all of these to OFF, since any of them might try to “phone home” while you’re out in the field. Pay attention to the pointer icons next to each service, since they tell you which services are actually being used: purple icons indicate recently used services, gray icons appear next to services that have been used in the last 24 hours, and purple outlined icons appear next to services using a geofence.

  • Settings > Mail, Contacts, Calendars > Fetch New Data: Switch Push to OFF if you don’t want these three services trying to shove data at you when you’re out in the field. Personally, I also have Fetch set to Manually, so no communication can take place unintentionally. Even then you’re not finished, though; tap Advanced to move to yet another screen with yet more Push-related settings. Tap each service in turn to set it up. For example, I’ve set iCloud to Manual and my Mail accounts to Manual here as well; I do not understand why this advanced setting exists or how it can be allowed to override my Push and Fetch settings from the earlier screens, but I am taking no chances.

  • Settings > FaceTime: Set Use Cellular Data to OFF. Clearly a video conversation via FaceTime running over the cell data connection is going to be disastrously expensive.

  • Settings > Safari: Scroll down to see Use Cellular Data; switch it OFF. Note that this doesn’t claim to prevent Safari from using cellular data; it says merely that it prevents Reading List from syncing data via cellular. I’ll have more to say about this later.

  • Settings > iTunes & App Stores: Scroll down to see Use Cellular Data; switch it OFF. This actually applies, it appears, only to iTunes Match and automatic download of items newly purchased on other devices.

  • Settings > Music > Use Cellular Data: This switch appears only if you have iTunes Match turned on. Switch it to OFF to prevent iTunes Match from downloading music via cellular.

  • Settings > iBooks: Switch Online Audio & Video to OFF. (Not everyone may have the iBooks app.)

  • Settings > Podcasts: Although we can’t recommend Apple’s Podcasts app, it’s likely that lots of people have it. If so, switch Use Cellular Data to OFF, but note that it applies only to automatic downloads. More on Podcasts later.

There may be other significant settings I’ve failed to list here. The important thing is not the list itself, though, but the process. It takes a lot of hunting and pecking and scrolling to ferret out all these settings! It’s almost as if Apple didn’t want to you to find them, though it’s more likely that no one at Apple has given the problem any thought at all. Plus, some of them seem to duplicate others, so that, for example, you may think you’ve turned off automatic Mail fetching in one place, only to discover that it is still turned on in another. It’s a jungle out there.

The System Might Be Buggy -- We come now to an area that is rather controversial and, more to the point, largely out of your control. It is, however, close to the heart of the matter. There is reason to suspect that iOS 6 may be violating Axiom 2: that is, that it uses cellular data even when you are home and connected to Wi-Fi. And it may be doing this despite any of the settings I listed in the previous section.

For example, one day recently I was using Mobile Safari to watch a YouTube video at home over Wi-Fi, and discovered later (by inspecting my usage, as explained earlier) that about half the data had apparently come over the cell radio. This is definitely not how I expect my phone to behave, and moreover there doesn’t appear to be any setting allowing me to switch off this behavior for Safari. Safari’s Use Cellular Data switch, which I mentioned earlier, claims to be confined to Reading List sharing across iCloud.

However, that switch was in fact ON at the time this YouTube incident occurred. Since then, I’ve switched it to OFF, and the problem has not recurred. (Nor have other members of the TidBITS staff been able to reproduce the problem, even with that setting ON.) Which leads me to the following speculative question: What if the label on this switch is incorrect and it doesn’t apply just to Reading List? In other words, what if setting this switch to ON somehow gives Safari license to use cellular data generally while on Wi-Fi? I’m not suggesting that this would be intentional on Apple’s part, but it could have something to do with the behavior I and others have witnessed.

And that, in turn, brings me to the most speculative point of this article. Please bear in mind that it is speculative! I have no facts and no hard data, and I’m not trying to spread uncertainty or rumor. But the truth is that during the beta-testing period for iOS 6, developers saw in Settings a switch that apparently allowed iOS as a whole to use cellular as a supplement to Wi-Fi even when Wi-Fi was present. So, let’s say, for example, that you’re watching a YouTube video, and that your home DSL, while decent, isn’t fast enough to prevent a pretty long delay before the video can start. iOS might, if this switch were set to ON, reason to itself: “Gosh, I could help this fellow out and start the video sooner by pulling some of the video down over the cell network.”

That switch is no longer present in Settings, so don’t bother looking for it. But what if — and remember, this is pure speculation — what if it was removed because Apple had decided this was such a great feature that they could just safely leave this setting turned ON behind the scenes? In other words, what if iOS 6 now deliberately and automatically uses cell data to supplement Wi-Fi, and you can’t prevent it from doing so?

In any case, even if Apple decided against leaving that switch turned ON when they pulled it, who apart from Apple can say that the code underlying that switch isn’t still present in iOS 6 in such a way that it could become active in certain situations? It is never safe to assume that developers always know how their programs will operate, especially when the heavy lifting is being done behind the scenes by the massive Cocoa Touch framework; and with something as complex as iOS, there are plenty of unexpected behaviors of which developers know nothing and for which they cannot be held responsible.

Some Apps Might Be Evil -- Some apps, by their very nature, can require massive amounts of data transfer. These are exactly the apps that one would wish to be most stringent in their adherence to Axiom 2. If iTunes Match or the Podcasts app downloads an entire gigabyte of data, which can quite easily happen, one might argue that you have only yourself to blame if you deliberately initiate such a download when you’re out in the field; but when you’re home, you expect Wi-Fi to be used exclusively. I have just said, however, that I suspect the system of possibly using cellular even when Wi-Fi is present. Under those circumstances, such an app could be a disaster (that gigabyte of data would cost me something like $60, and we’ve heard reports of 8 GB of data — $240 — being downloaded without the user’s knowledge or intention).

But we can go further. Such apps may come with a Use Cellular Data switch in their settings, and you may have turned this switch to OFF. But what if the app fails to pay attention to that switch? This might be because the app has a bug, or it might be because of the speculative system-level bug I hypothesized in the preceding section. I do know, as a developer, that iOS 6 has a new developer-level feature where, when your app places a request over the network, it can specify whether or not that request may be satisfied using cell data. Well, what if that feature is broken internally at system level, so that I (the developer) believe I am turning cell data off for my app in response to you (the user) setting a switch, but in reality the system is using cell data anyway — and, perhaps, using it even when Wi-Fi is present? You can see that in that case we’d be in a pretty pickle.

There is no doubt that the Podcasts app and iTunes Match are in fact responsible for some of the very large cell data usage of which users are complaining. Recall that, as far as TidBITS is concerned, this entire thread started in an article by Glenn Fleishman (“Does Apple’s Podcasts App Suck Cellular Data?,” 17 September 2012) in which he observed cell data usage that he attributed to the Podcasts app. And this was before iOS 6 had shipped. The Podcasts app, of course, comes from Apple, so who knows what private system-level features (or bugs) it accesses behind the scenes? In any case, the Apple Discussion thread I mentioned earlier gives the impression that you can get massive cellular data use from the Podcasts app no matter how you set that switch.

Adam Engst, who still has DataMan Pro to give him some idea of which processes are using cellular data on any particular occasion, has made some further observations. He can demonstrate, for example, that the Skype app can use up to 2 MB of cellular data per day, just by existing in the background. And it can do that even when you’re on Wi-Fi. It’s not a lot, granted, but 15 to 30 MB of data out of 200 MB per month for just having launched Skype at some point seems excessive.

Another problem is that you don’t really know the meaning of the choices you’re making in an app’s settings. Adam has observed that the Podcasts app can suck down cellular data even when the Use Cellular Data switch is OFF, evidently because that switch applies only to automatic downloads of new podcast episodes, not manually initiated streaming. Assume, for example, that you have the first episode of a podcast downloaded, but not the second. When the first finishes playing, the second may start playing automatically, and even if it doesn’t, you might navigate to it using other audio playing controls, or even play it from the Podcasts app without noticing the little download icon. That’s a good way to use up tens of megabytes without noticing.

Conclusions -- Although not every iOS 6 user is seeing a problem, there’s no doubt in my mind that a problem exists, and that the fix must come from Apple, possibly in conjunction with the phone providers. (Apple even implicitly acknowledged this with a carrier settings update for Verizon Wireless users that prevents the iPhone 5 from using cellular data while on a Wi-Fi network.) iOS 6 does use more cellular data than previous systems did, and it appears to use it in circumstances where previous systems did not.

A couple of days ago I restored my iPhone to a completely clean iOS 6 and went through all the settings I could find and turned everything off that might influence cell data use, except for turning off the master Cellular Data switch. Even though I was home with Wi-Fi the entire time, a couple of hours later, there had been some cell data usage. Even during the two hours it took me to draft this article just now, with my iPhone sitting unused beside me (except when I picked it up to navigate the Settings app so I could describe the location of the various switches), there was some rise in the reported cellular usage. These were not large amounts, but that’s not the point: the point is that the amount should be zero and it isn’t.

But this is not the worst. Reliable-looking experimentation has demonstrated that certain processes such as iTunes Match and the Podcasts app can download huge amounts of data over the cell network, even when you think you’ve told them not to. Glenn’s article referred to this very sane-looking, very scary blog post by John Herbert. Josh Centers has put up a video demonstrating that iCloud can leak cell data at the rate of 1 KB per second, even if every iCloud service is turned off. And, of course, clouds of witness have gathered at the Apple Discussion boards — the one I referred to at the start of this article, and this one, and doubtless many more.

Something must be done, and I have little doubt that it will be. If the posts at Apple Discussions are to be believed, users have not been hesitant to call their cellular providers and complain of unwanted cell data usage. The cellular providers, in turn, are surely talking to Apple. (And so too, I bet, are their lawyers. It wouldn’t be surprising to see a class action lawsuit against Apple with regard to these unwarranted charges.) In the meantime, if you’re having similar problems and can quantify and document them, I remind you that you can tell Apple about it at their iPhone feedback Web page.

Finally, Adam Engst (who, after all, publishes TidBITS and always gets the last word) encourages me to encourage you to request that Apple allow DataMan Pro to be sold in the App Store once more — even though I, Matt, think there’s a snowball’s chance of that happening, since to do what it does, DataMan Pro must surely be using undocumented APIs that the App Store explicitly excludes. Still, Adam has a point. What makes this problem so mysterious, after all, and so difficult to report clearly to Apple, is that most people who are experiencing it cannot identify which apps are at fault. While DataMan Pro may not be perfect, it provides precisely that information.


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Comments about Mysterious iOS 6 Cellular Data Usage: A Deeper Look
(Comments are closed.)

A full restore seems to have solved my problem which was similar and massive - AT&T 4GS
Dan Ho  2012-10-26 19:32
I've noticed, for some weeks now, that nearly every time I wake up my iphone, the "navigation services" indicator comes on for about 20 seconds. I was finally fast enough to discover that it's Passbook. I suppose it is checking to see if I'm at Wallgreens? Starbucks? Target?... so it can decide if an applicable pass should be popped up.

I know "location" is determined using GPS (not data)... but Passbook surely needs to compare my location against a live database of potential live-spots... and that must consume data.

I imagine this is small for each transaction... but it seemed to happen a hundred times per day (nearly every time I lit up the phone).
Richard Totaro  2012-10-26 19:47
When an iOS device is "asleep", it drops its WiFi connection and falls back to cellular data. This may explain why there is still cellular data use while a device is within a known WiFi network.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2012-10-26 20:11
Apple doesn't document that behavior, and it ostensibly happens only when a) it's not plugged in to a power source and b) when it's not sending or receiving large amounts of data.

Because it's not documented, my understanding of this is based on extensive reading of people's reported tests in the Apple forums, and the fact that prior to iOS 6, this excessive cellular usage didn't occur while a device was in standby mode.
Matt Neuburg  An apple icon for a TidBITS Staffer 2012-10-26 20:14
I've seen this claim in connection with the problem described by the article (e.g. on Apple Discussions), but I regard it as a canard. There is absolutely no reason why it should be true, and it doesn't accord with how my device behaved under iOS 5. If it's true of iOS 6 (which I don't necessarily believe), it's part of the bug I'm describing.
Steven Fisher  2012-10-26 21:13
I thought I remembered reading about this in Apple's developer documentation, but I can't find it.

The only relevant bit I found is that if an application doesn't set UIRequiresPersistentWiFi, the wifi hardware will be turned off after 30 minutes. I can't imagine why this would be the case if the app is still actively using networking, however.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2012-10-26 21:22
Exactly — I thought it was documented, too, but either it was removed or never existed.
Matt Neuburg  An apple icon for a TidBITS Staffer 2012-10-26 21:40
It *isn't* the case if the app is still actively using networking. UIRequiresPersistenWiFi is highly technical, rarely used, applies only to individual apps and only while they are running, and has nothing to do with the case.
Jonathan Lundell  2012-10-26 20:46
AT&T's myAT&T app is decent for tracking usage, especially if you have multiple devices on a shared plan.
Ashley Ward  2012-10-26 21:32
I wonder if analysing this using Remote Virtual Interface would reveal anything? As far as I understand, this allows iPhone network traffic to be routed via a Mac for debugging. I haven't tried it, and don't know if it allows traffic to be segmented as destined for cellular or WiFi, though. See
artMonster  2012-10-26 21:33
If this issue is a software bug, it will eventually be fixed. If it is behavior that Apple thinks is the proper way things should work, then the bigger issue is that Apple will have to limit usefulness and innovation. Imagine that when the Interstate Highway System was built, all the freeways were tolled, and charged per mile driven. The U.S. would have developed very differently.
Chris Pepper  An apple icon for a TidBITS Staffer 2012-10-26 23:05
Thanks for the pointer to *3282#. Note that if you see a (Deactivated) usage line it might be usage from a previous cellphone -- I am told it will go away next month when my 4S has aged out.

Annoyingly I see Amy and I have used 36 text messages this month, for $7.20 so far. But AT&T doesn't have a plan under $20 (unlimited), so we'll continue being nickel & dimed.

If only my coworker would swap out his Android phone! I never thought about how effective the financial motive is at getting iMessage users to be brand evangelists.
Matt Neuburg  An apple icon for a TidBITS Staffer 2012-10-26 23:59
Chris: We're getting a bit off topic here but yes, I've had AT&T turn off text messages entirely, and so I can receive text messages only from iPhone/Mountain Lion users, and that's the way I like it. :)
Adam Engst  An apple icon for a TidBITS Staffer 2012-10-27 11:16
That explains why, when you had cellular data OFF while coming to get me at MacTech, you didn't see my message to you. We had an iMessage connection, but when I sent it, it turned green to indicate that it had gone via SMS, but then you didn't get it at all because of that. Fascinating!
Anyone who upgraded from iOS 5 via an OTA update should perform a general -> reset -> "reset all settings" as there are a number of things that can get messed up during the update. I did so because of glitches I was having on my iPhone and iPad and it fixed them.

That said, there's also a little known fact about the way iOS works with respect to data. If an app is downloading over the cellular network, it won't automatically switch to Wi-Fi when a Wi-Fi connection is established. That means if you start streaming video or audio while out and about and then go home, the app will continue to use cellular data until you stop and start the stream. That can cause unexpected usage.

Finally there's speculation that iOS 6's IPv6 support can cause cellular data to be used if the Wi-Fi network in use doesn't support IPv6, but an IPv6 address is requested.
I know this is tricky, and information is contradictory, but I wonder if it's a carrier-specific problem; I'm in France, and perhaps this is only happening with US carriers?

When I first read about this, I reset my cellular usage statistics; that was October 2. I looked this morning, and I have a total of 55 MB used since then, so there's obviously not much of a leak. I work at home, so I don't use cellular data very often, except when I'm waiting in doctors' offices or the like, or when I'm on the road and need to look up something.

Randy Drawdy  2012-10-27 06:49
My 2 one year old iPhone 4Ss are using cellular data when in range of wifi at one hour intervals 24/7, according to's website usage detail. On Thursday 10/25 Apple replaced both phones with new ones from the local Apple store. I didn't restore from backup and only redownloaded a few apps to minimize resemblance to the old phones. The new phones are exhibiting the same behavior.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2012-10-27 11:23
AT&T's billing is either in about 20 MB increment or hourly now, I think, so it's not that it's using it in one-hour intervals: that's the accumulated usage during that period of time.
Vanessa  2012-10-27 09:57
I have five iPhones, different models, all on ios 6. Four of them send data every hour with as much settings turned off as possible. The 5th one doesn't but it is two states away at college. So I'm wondering if it is something with the network in my area?
Wynne Krangle  2012-10-28 13:31
I began to have similar problems with my iPhone 4 when I switched to iOS6, but it also included extreme battery usage. The data usage is at its worst when I travel and have to depend on cellular connections.

I have twice phoned my service provider (Bell Canada) and twice been to different Apple stores. Bell gave all kinds of excuses which implied that the problem was me and my way of using the apps. Even though I pointed out that my usage spiked by hundreds of MBs at times I was either asleep or else arriving off an airplane and right into immediate cell usage, Bell really just gave me the brush-off.

The people at the Apple stores ran a series of diagnostics and told me everything was fine but suggested I needed to reset my phone. I did that both times but each time was then going back home where this is not such a problem.

In 10 days, I am off on another trip and will be watching very carefully.
Mike Labadie  2012-10-28 20:09
Rogers reps are doing the same. First rep I got was VERY condescending. "We'll, OBVIOUSLY, sir, YOU have downloaded an APP that is using that data, or you have changed how you use the phone. All the data use is valid and chargeable." So why, then, did the second rep I talked to IMMEDIATELY offer (actually, set without even asking me) two months unlimited data to 'help you and us have time to figure out what is going wrong...' I coulda kissed the guy! (He might have felt that a little weird though)
Jim Ledvinka  2012-10-29 20:59
I wonder why nobody has mentioned the possibility that (perish the thought) the increased cellular data usage in iOS6 is intentional on the part of Apple and its cellular partners.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2012-10-29 21:17
Seems unlikely for two significant reasons.

First, people who feel overcharged unreasonably make a stink, possibly cancel service, complain to the feds and attorneys general (who have often forced carriers into settlements), etc. It's so egregious that if it were intentional, it would be exceedingly unwise.

Second, if this were intentional, it would involve collusion among many people, including Apple engineers, and likely rise to the level of criminal conspiracy. Given the amount of money and number of customers, a lawsuit could result in billions in damages and criminal prosecutions.

If it's intentional, it's by a number of people who have no sense of how they might receive justice. Forget ethics. It's just too easy to show that this is unintentional behavior by users.
Matt Neuburg  An apple icon for a TidBITS Staffer 2012-10-29 22:51
Gosh, I thought I was suggesting that this *is* intentional on Apple's part - not as a some sort of collusion to make you spend more money, but intended as a good thing, namely to make your "poor" Wi-Fi connection faster by supplementing it with cellular. I think they just failed to do their homework about what sort of Wi-Fi connection most people have at home and what sort of prices they pay for increased cellular data use. So, yes, I think it's intentional but misguided.
Adam Engst  An apple icon for a TidBITS Staffer 2012-10-30 10:10
What's interesting is that if we were back at Day 1 of the iPhone, where everyone had unlimited data for $30 per month, making it so the iPhone used Wi-Fi and cellular simultaneously to improve the user experience would be utterly brilliant. It's only because it's in some way consuming a scarce and expensive resource that it's a problem.
JohnB (SciFiOne)   2012-10-30 01:34
Out of curiosity, I reset the cellular usage to zero on my iPad (3) running iOS 5.x on Oct 26 at 4:30 PM. At 10:30 PM Oct 29 it had sent 91kb and received 167 kb via cellular. It has not left the house WiFi zone the entire time. I had everything I can think of turned off. Next test I will use the article to see if there is anything else to turn off. (FYI -Haven't gone to iOS 6 yet because of an upcoming trip and lack of time to bebug any problems before leaving.)
Adam Engst  An apple icon for a TidBITS Staffer 2012-10-30 10:12
That minimal level (a few hundred KB over a few days) seems entirely reasonable to me. It makes sense that iOS would need to do the occasional check-in to see if cellular data was available, if only to know how to display the proper icon in the status bar.
JohnB (SciFiOne)   2012-10-30 19:02
I agree. It's only about 100KB/day. A very small amount of even the minumum cell package.
JohnB (SciFiOne)   2012-10-30 19:03
Gives me a reference point to compare against after I start using iOS 6 in a couple of weeks.
JohnB (SciFiOne)   2012-10-30 12:01
Used 14KB both ways overnight when no was using it.
Freek Dijkstra  2012-10-31 12:05
The problem is also taking place in Australia, UK and the Netherlands. The main issue is that iOS does not tell the user it's using the expensive cellular connection. Same with Facetime and iMessage -- everytime you turn on your phone, it sends an expensive SMS abroad to 00447786205094. (Edit: OK, "expensive" it isn't, typically $0.30 or so. I was a bit annoyed with Apple's policy when I wrote this. Added iMessage next to FaceTime.)
Freek Dijkstra  2012-10-30 17:24
So you might want to add Preferences > FaceTime to the list of things to turn off.
Freek Dijkstra  2012-10-30 17:51
I found another one:
Settings > iCloud >Documents & Data > Use Cellular Data
Larry Deckel  2012-10-30 23:56
I have experienced large amounts of cellular data being used at roughly the same time each evening, while at home where I have Wi-Fi. This happened every night. Based on some troubleshooting tips I read about - I deleted apple's Podcast application - and lo and behold, the nightly pulls of cell data stopped immediately.

There's no question in my mind that apples podcasting app is using cellular data without permission, even when wi-fi is available. Not sure why its doing this as my subscribed podcasts should only be updating once a week anyway (I only subscribe to a couple). But it seems the app either downloads the same podcasts every night, or does something that requires pulling a lot of data via the cellular network every night. Even when wi-fi is available and I've explicitly asked it NOT to use cellular data.

Deleting the app solved the problem for me completely.
(FYI -- I do not have iTunes match turned on, on my phone - so happily, that wasn't a contributing factor.)
Larry Deckel  2012-10-30 23:59
By the way - I am on AT&T.
And interestingly, for the last week, logging into the AT&T site to check my data usage I get a message saying they cannot give me details of my data usage.
I wonder if AT&T and apple are trying to work out what is happening. (I do know however, by asking for my data usage over the phone (rather than the website), that the consumption almost completely stopped after I deleted apple's podcast app.
Freek Dijkstra  2012-10-31 10:09
FYI, I found another App that counts the network usage *per application* (like DataMan Pro), called Onavo count. It's free but does ask for your provider and installs a profile with a custom APN (cellular data configuration).

My provider contacted Apple, who replied "there is no known problem".
I also phoned Apple. Their advice was to turn of "Wifi and cellular". Surprising, since that feature was removed from beta. It's not in the final release of iOS 6. After telling him that, he suggested to turn off "Cellular data" altogether. The person I talked to agreed that was not an ideal solution (to say the least), but I don't have the illusion that his opinion has any say upstream at Apple.
Adam Engst  An apple icon for a TidBITS Staffer 2012-10-31 12:14
Yes, I just ran across Onavo Count too and am testing it against the others... It's a very different approach with the two profiles it installs - we'll see if it can provide the app-centric data we need.
Bruce Hiland  2012-10-31 10:28
We had this problem in spades on one of our two iPhone 4's upgraded to ios6. The major culprit turned out to be the "documents and data" setting on iCloud which bypasses wifi running up the data usage dramatically.
Apple really needs to re-think all the "gee whiz" features impact on their customers' data budgets! Long overdue!
Freek Dijkstra  2012-10-31 12:14
There are so many better ways. As Matt clearly pointed out, there should be a global option to limit the cellular data usage. Here are a few suggestions for useful options:

* Limit the amount of cellular data per day/week/month, and automatically turn it off when the limit is exceeded.
* Only allow cellular data for the frontmost application (disable eg email push on the road, unless you check manually; also disables background syncs).

(Advice I got from the Apple engineer: tap home button twice to see the open applications. Press and hold to force quit.)
Steve Rothman  2012-11-02 11:16
I haven't heard of this problem - but I think APP UPDATES can slam users. I got hit with a mysterious 400GB data usage with my iPhone 6 (Verizon) one evening in the space of about two hours when I wasn't really doing anything with the phone except for light email. No proof, but I believe what happened is that I had initiated the updates of several apps (including nav apps with big maps) that morning while I was on WiFi - but the updates stalled and I didn't think any more about it. I keep my cell data off during the day because my office has great wifi. But then in the evening I turned it on so I could check my email during my commute - and I think in the space of a couple hours LTE sucked down several huge app upgrades. Users definitely need better/easier control of cell-data usage!
As suggested in the article one approach to track approximate data usage is Settings > General > Usage > Cellular Usage. In my experience, however, even this tool is totally meaningless.

I have attempted to use this tool several times on my iPhone 4s while traveling internationally on a limited roaming plan. After resetting the data to zero the amount of data usage measured does increase. So far, so good. However, I have sometimes checked and seen the numbers DECREASE from their previous values, often by tens of megabytes. Later on they will be up again. Then down. It makes no sense whatsoever.

I started to wonder if I was just imagining this or losing my mind so I started taking screenshots of that page every few hours. I now have a chronological series of screenshots that show that I'm right. Data values are all over the place and often as not go down and not up!
Freek Dijkstra  2012-11-03 08:31
Dale, would you mind publishing these screenshots?

On a related note, those who have not done so: Apple released iOS6.0.1 last Thursday ( ), which include these bug fixes:

• Resolves an issue that prevents iPhone from using the cellular network in some instances

• Consolidated the Use Cellular Data switch for iTunes Match
Bokonon  2012-11-05 02:12
How can a podcast be 1gb. I also have watched vimeo movies over cellular and it says that my usage was 200 mb for a movie that in the download section is no bigger than 45 MB. This is bull and I'm getting pissed.
Greg C  2012-11-05 20:13
Back when I first got my iPhone 4, there was plenty of data "leakage" that I could not explain.

After turning all notifications off and all cellular data options off, I was still getting leakages that said I was using close to 1MB in a single day, without even touching the phone. I presume there must be some data transfer in order to establish connections with cell towers. Riding on subways that establish and lose connections at every stop was what I put it down to, but that is just a guess.

If Apple is using cellular to boost poor wi-fi or switching to cellular when out of wi-fi range, even with cellular options turned off, well that is the stuff of lawsuits.
Brian Hannon  2012-11-06 09:53
Some of this seems to be intentional and directly related to the user experience. For example, leaving Skype running, of course I want it to update my status, know when I receive an IM, and know when somebody is trying to call. To do that, it needs data, whether I've never moved from my desk where, presumably, it's been connected to wifi all day (though not for sure, wifi isn't 100% reliable) or whether I'm out and about when much of the time I'm on cell data.

I have dozens upon dozens of Apps, many of which need the same type of "constant" connectivity as described above for Skype. In addition to system-level things from Apple: if one of my friends wants to know where I am, FindFriends is gonna access data, cell triangulation, and GPS all without me knowing about it.

Frankly, 200MB/mo isn't enough for a good modern experience, unless you never leave your house. And if you do go out you should use the "cellular data" switch in settings. Worrying about apps using tens of K is silly.
Adam Engst  An apple icon for a TidBITS Staffer 2012-11-06 10:17
You're absolutely right that worrying about tens of kilobytes is silly, but that's not what's at issue here. We're talking about usage patterns in the tens and hundreds of megabytes, and some people are seeing usage in the gigabytes range.

200 MB per month was just fine under iOS 5 for me and many others. Many people do not use significant data outside of Wi-Fi range and don't see the need to double their monthly data bills for no change in behavior.

Matt Neuburg  An apple icon for a TidBITS Staffer 2012-11-06 10:33
200MB/mo was plenty under iOS 5; I never came close to hitting that limit. If iOS 6 puts me in constant danger of hitting the limit, then something has radically changed for the worse - and that's the point, since this is exactly what has happened to many users.
Brian Hannon  2012-11-13 05:27
I'd argue that even worrying about tens of megabytes doesn't make sense anymore. There's good reason that AT&T no longer sells a 200MB data plan.

It's my understanding that the hundreds of MB and GB usage that some people saw was a specific bug which Apple has fixed, related to switching / sharing between wifi and 4G. And that's not what Matt's talking about above.

The article above, and many of the comments, talk about tens of megabytes and less, and present an awful lot of speculation with very little actual data or even information about what features in iOS do. I don't think it's really helpful.
Brian Hannon  2012-11-13 05:25
That's a good point and something you need to consider when choosing to stay with a legacy data plan that ties you largely to wifi. I think that by adding features in the new version of iOS, Apple adds value which worth the increased data usage and it's why carriers are constantly upgrading their capacity. Sticking with 200MB would be, to me, like insisting a 28kbps modem is still okay when the rest of the world has gone to broadband. But that's a choice for you, and apparently, many users. You'll need to really go into detail with a data-monitoring app and figure out which of the features you can't afford to use.

I've been in Europe this month working with a 500MB limit prepaid SIM (most months in the US I easily burn 2-4GB). I've been surprised if I limit my use of mapping and social networking I can keep to 10-30MB/day. But then I hit "update all" apps while in my office and 15 min later walked to lunch losing the wifi and spent 100+MB all at once. Whoops!
Adam Engst  An apple icon for a TidBITS Staffer 2012-11-13 09:14
Alas, it is not true that the hundreds of megabytes and gigabytes of usage is a specific bug that was fixed - you're probably thinking of the Verizon-specific carrier settings that Apple released that is mentioned in the article. It likely addressed issues for Verizon users, but did nothing for everyone else.

A reader just sent us a usage chart from a friend of his who in the last year has used between 200 MB and 500 MB per month. In the last month (November on his chart), he used 2.9 GB. This particular guy doesn't care because he's retained his legacy unlimited data plan, but it seems fairly clear that something has changed in iOS 6.

And the reader who sent us that chart from his friend was doing so because he used 200 MB of data 7 days into his month with no change in habits.
Adam Engst  An apple icon for a TidBITS Staffer 2012-11-13 09:23
Hmm, I'm not sure I can agree that Apple is in any way justified in adding features to iOS that will consume cellular data without my knowledge or permission. I can't see how that improves the user experience in any way, and if it were true that Apple has done this intentionally, I think they are opening themselves up for a a serious class action suit for causing excessive charges to what could be millions of users without warning.

Your story is a perfect example. I don't know how much your 500 MB pre-paid SIM cost, but is it a better experience that you got your apps updated right at that moment, or that you paid so many euros (and potentially had to fuss with getting another SIM) because Apple allowed a process that started on Wi-Fi to continue on cellular without permission? Seems to me that any user experience design decision that costs the user money without warning is the one that should be cut.

I have gone into app-level detail with the old version of DataMan Pro, and I can say with assurance that the Podcasts app will use megabytes (and up to tens of megabytes, but not hundreds) of data when it shouldn't. I haven't experienced the truly egregious data usages, though, so I haven't yet been able to identify the smoking gun for the larger usages.
Matt Neuburg  An apple icon for a TidBITS Staffer 2012-11-13 09:59
I'm not talking about tens of megabytes and less. I'm talking about experiences like this one: These reports continue to pour in (37 pages of on this thread so far), and no, it is not fixed. Just because some people are not experiencing the issue doesn't mean it doesn't exist or isn't a serious issue.
Ben Ing  2012-12-06 22:42
After I received my iPad mini AT&T LTE a couple of weeks ago i decided to move to the 6GB shared data plan since we had run into a couple of minor overages on my kids' iPhones, A couple of days before my billing date, I woke up to multiple AT&T overage messages even though I had been using wifi and was within 6 feet of my Airport. Checking the usage on myATT I saw that I had used 13 GB. Calling AT&T, they told me the iPad switched over to cell data when it was asleep and an app must have run in the background. Looking through the AT&T logs, it said i was downloading approx. 19.5 MB every minute from 10:00 pm until I woke up at 7:00 am! Luckily, they reversed the charges, warning me to shut down all applications overnight to prevent any inadvertent charges. Now, here's the strange part - when I check cell usage in the Apple about window it says I have downloaded a total of 2.3GB (never reset because it's new), while myATT shows 14 GB. So who's lying?
Adam Engst  An apple icon for a TidBITS Staffer 2012-12-07 08:03
Gah! Well, regardless of who's lying, it's AT&T who would be charging you, so it was good they reversed the charges. But shutting down apps at night is just plain nuts - just as turning off cellular while you're connected to Wi-Fi is nuts.
Matt Neuburg  An apple icon for a TidBITS Staffer 2012-12-07 08:36
Did this happen on or about the last day of the month? If so, this is probably a different and long-standing issue with AT&T, and not the new iOS 6 behaviors discussed in this article. It's happened to me and to many others, and there are long threads on Apple Discussions about it. My cynical theory is that it's just a cheat by AT&T to see if they can get some extra money; if you complain, they wipe the charge and no harm done, but if you don't, they make some free dollars. Some people have a more technical explanation (they are updating some kind of phone-related firmware or software during the night but accidentally charging you) but I don't buy it.
Ben Ing  2012-12-09 22:53
Yes, it was overnight 2 days before the end of the month. I'd love to read through the Apple discussions about this if you have any links or search terms.
I too am happy that AT&T reversed the charges, but I am concerned with the same issues in the future, especially after getting the warnings. Luckily, I have been grandfathered in with an unlimited data plan that has carried forward since my first iPad, and was attached to my iPad 3. It was a hassle due to the new microSIM, but I went to an AT&T and had them swap SIMs since my iPad mini is now my primary device (still holding on to the iPad3 though, along with my Apple Wireless keyboard.
I had considered moving the unlimited plan over to the shared plan since I rarely got through much more than 2 or 3 GB/month (the charge is a wash), but after this escapade I'll be holding on to my unlimited data plan as long as I can.
John vivian  2012-12-09 12:33
I innocently accepted a download of IOS 6 on an employer supplied iPad 2. The first month my data usage was up over 500 percent. The office manager pointed it out to me. My usage pattern had not changed. The second month I was presented with a bill by my employer for $155 for excess data charges. If this cant be fixed I'm turning the thing in.
Adam Engst  An apple icon for a TidBITS Staffer 2013-01-03 15:21
This article also points a finger at some sort of problem related to an Exchange account - the affected iOS devices were checking via Wi-Fi and cellular every 2-3 seconds. It's not universal, but if you're still seeing data problems and have an Exchange account (which could be for Google too!), consider disabling it to see if that helps.

This is likely unrelated to any changes in iOS 6.0.2, but this guy found significantly battery drain and data usage with an Exchange account, so anyone experiencing problems and using an Exchange account should look into that.
Adam Engst  An apple icon for a TidBITS Staffer 2013-04-11 10:28
Our AirPort base station went offline last night, and Tonya's iPhone chewed through 380 MB of cell data before we woke up. Podcasts isn't on the iPhone any more, and she had reset the networking settings the day before. Something is clearly still happening in iOS 6.1.3.

AT&T happily refunded her the money when she asked, but then forwarded her to a tech support guy who cluelessly blamed it on weather apps, news apps, and automatic updates. It's clearly a bug in iOS 6, and whatever Apple has done to solve it for some people, it keeps coming back to haunt others.
Adam Engst  An apple icon for a TidBITS Staffer 2013-05-28 11:20
The problem continues - here's a Forbes article discussing how Apple and AT&T aren't talking about it: