iPhone no longer charges from non-Apple accessories if locked

Hi Adam & Josh

I just sent this feedback to Apple:

Yesterday I updated my iPhone to 11.4.1. I plugged it into my Belkin dock as usual in the evening. In the morning it was only at 30% charge so I thought I hadn’t docked it correctly. However this evening when I docked it I noticed the message “Unlock iPhone to use accessory” and the phone was not charging. It only charged after I unlocked it. This unannounced and pointless change is a serious personal safety issue as people like me will assume their phone is charged for the day. Please reverse the change or at least make it a selectable option.

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It was announced and is not pointless. It’s USB Restricted Mode and it was discussed as an upcoming iOS 12 feature but was delivered early in the 11.4.1 update. TidBITS linked to an article about USB Restricted Mode in The Verge. Its primary purpose is to protect against passcode cracking tools. It can be turned off.

Using USB accessories with iOS 11.4.1 and later - Apple Support


Seriously? Apple decided not to allow charging over USB accessories as well as locking out all the other functionality? That makes no sense to me… unless there’s some odd configuration in the controller chip that can only do all or nothing.



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It does allow charging, but the Belkin accessory must be trying to access data over USB that a normal charging cable/charger does not.

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Sounds like this would be a good topic for an article, @jcenters.

Anecdotally, my iPhone X still charges when I plug it into my car’s USB port (while it plays music).

I also have a Samsung wireless charger thingie, it still works.

The Belkin must be doing something different if it no longer works as expected.


and for the record, I whole-heartedly support Apple’s decision here. This was a potential security breach vector that iOS is addressing.


Or maybe the cable. If off off brand it may not have a “real” lightning security token.

Thanks for the link Curtis - I did try searching the Apple Support webpages for this advice without success. So my apologies to Apple. I have now switched on USB Accessories support (but will take care using unknown accessories as usual).

The odd thing is that Belkin Dock is just supposed to a charging station - it has no other function - and it was apparently Apple-certified when I bought it many years ago. I have found it very handy for video conferencing since the iPhone is upright and still charging.

At work I have a Twelve South’s HiRise 2 Deluxe that’s nothing but a metal stand with their Lightning cable threaded though it and I’ve gotten the message on it as well. I notice the message and don’t mind pressing the TouchID to unlock it.

At home I have an old Apple dock with a 30-pin to Lightning adapter, I don’t recall if I’ve seen it there; since that’s where it charges overnight, missing the message would be a bigger problem.

Edit: Unsurprisingly, the home dock + adapter can trigger the message as well.

I’ve seen the message when I connect to a Lightning Cable attached to a computer or my iHome Clock Radio but not when connected directly to a ‘dumb’ charger (Apple or Anker).

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I’ve written an article that explains what’s going on https://tidbits.com/2018/08/06/usb-restricted-mode-can-block-ios-device-charging/

It is a security measure. Being asked to open my iPhone before backing up, uploading, downloading and sometimes charging isn’t that big of a deal when you think about it from the security issue. I don’t think it is entirely a device to force us all to buy Apple branded accessories. I admit that I resist some of the wrong headed, lazy programming that has plagued recent developments by reinstalling older versions of Apps that have taken a turn for the worse and I use a mid 2012 Macbook Pro and a SE iPhone 6 because they are more useful than the newer stuff, but the charging thing makes us more secure.

I experimented with different computers and USB block chargers and docks. What I found was my MacBook Pro 17" and 15" and the Lasuney dock all result in the error message but if I used the same cables plugged into an Apple or a generic power block the charging worked just fine.

Yes, this is nothing new. A dumb charger (like a power brick or a cigarette lighter adapter in your car) will charge it just fine. Any USB connector that includes data (computer, a dock, a car stereo’s USB AUX port) will make you unlock the device even for charging.

Apple really should provide a way to tell the device to remember its attached device as an authorized one so only have to authorize it once, but so far they have not done so.

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Yes, more than once I’ve run a device down to minimal charge, plugged it in for the night, and gotten up the next morning to find it had… minimal charge. Because I hadn’t looked at it when I plugged it in so didn’t notice it required unlocking. It doesn’t do it all the time, only occasionally. And it’s not just non-Apple accessories, I’m using the cables that came with the devices plugged into an iMac.

I’ve since switched to charging my iPhone using a wireless charger, so no longer have the problem with it, but still do with my iPad. It’s happened often enough I now remember to check, but it seems to me the clever engineers at Apple could allow charging without unlocking, and just block data until unlocked, but I’m not an EE, so maybe there’s some good reason it can’t be done that way.

I am sure that the reason is to make absolutely sure that data cannot leak through the port if the phone is locked due to an unknown security exploit. As Josh details in his article, there is an easy way to get around this: as you did with Qi charging, or by going into settings / Face ID & passcode (or Touch ID & passcode) and turn on the option to allow usb accessories while unlocked. If you’re unconcerned about your device getting into the wrong hands to access data through usb, you should be fine.

The problem with this is that for the phone to recognize the attached device it has to exchange at least a tiny bit of data with the device. That is, until the other device sends a reasonably distinct identifier, the Apple device has no basis on which to recognize it. (And “reasonably distinct” means “not spoofable”.)

The most secure policy is the one Apple has taken: exchange no data at all before unlocking. Anything else would have the potential for either device spoofing or an exploit of the recognition algorithm.


I could’ve sworn this was already the case; I have a large number of docks and dockable devices, some going back to 30-pin, and it seems to me that it was easy to “train” a given iOS device to “trust” a given dock. Occasionally when I introduce a new device or reintroduce a factory-restored device, I get the unlock message, but once completed, “remembering” the Dock isn’t an issue.

One thing I know for certain, is that at least on a per-app basis, the app certainly is capable of remembering its settings per-dock; e.g., JetAudio definitely remembers the preferred volume between three docks I use. Though, admittedly, I have run into many a dock that was a cheap, non-MFi-Certified device that required both unlock and a volume reset with each use.

I’m honestly confused how my personal experiences do not seem to align with others.

EDIT: I just realized I dropped in on a three-years old conversation; please disregard.