If you have connected an iPhone, iPad, or iPod touch to a USB accessory, or even a Mac or PC lately, you may have seen an “USB Accessory – Unlock iPhone to use accessories” message appear on the screen (or “Unlock iPad to use accessories” for iPad of course).

This message appears on screen due to a new security feature introduced in iOS, which aims to better protect iPhone and iPad from unauthorized access attempts by USB connections. This is mostly a good thing, but until you approve the USB accessory and unlock the iOS device, you may find that the iPhone or iPad won’t communicate with the USB accessory, or it might not even charge.

Resolving the “Unlock iPhone to Use Accessories” Message with USB

The simplest way to resolve this message if you see it on the screen of your iPhone or iPad is to unlock the iPhone or iPad using your passcode, while the USB device or USB accessory is connected to the iOS device.

You may have guessed that already based on the message itself, but once you unlock the iPhone or iPad with a proper passcode, the message goes away, and the USB accessory or USB device will be able to communicate with the iOS device as intended, including charging the iPhone or iPad as intended.

How to Disable the USB Accessory Unlock Message on iPhone or iPad

If you connect many different USB devices and USB Accessories to an iPhone or ipad you may decide you don’t want to see that “Unlock to use accessories” message anymore, and no longer want to unlock the device every time to deal with this. You can disable this protective mechanism in iOS settings, but realize that doing so comes at a theoretical security risk since it will allow USB devices to connect to the iOS device without the iOS device being unlocked.

• Open the “Settings” app in iOS
• Go to “Face ID & Passcode” (or “Touch ID & Passcode”)
• Scroll down and locate the “USB Accessories” setting and toggle that ON to disable the USB security restriction protection

By turning on the setting for “USB Accessories” you will no longer see the “USB Accessory – Unlock iPhone to use accessories” or “USB Accessory – Unlock iPad to use accessories” messages on the devices when connecting anything via USB.

If you have noticed that your iPhone won’t charge when plugged into some computers or devices and you’ve followed the usual troubleshooting steps to resolve charging issues, and the iPhone is running a modern version of iOS showing the ‘USB Accessory’ message on the lock screen, this very well could be the reason why.

What’s the point of restricting USB Accessories on iPhone or iPad?

Restriction of USB accessory attachments to the iPhone and iPad is a fairly new feature that is aimed at improving the security of iOS devices, by aiming to prevent unintended access of a device through any USB connection or USB mechanism.

A prominent example of what the USB security setting is aiming to prevent is something like the GrayKey box which is apparently used by some agencies and law enforcement bodies to gain access to otherwise locked iPhone and iPad devices, by revealing a devices passcode. But these capabilities are never limited, that’s just the nature of security flaws and exploits, and so if such a tool is available to the “good guys” then such a tool would also be available to the “bad guys” who could also gain unauthorized access to an iPhone or iPad, thus something like this poses a security risk.

Whether or not you want to keep the default setting with USB Accessories toggled ‘off’ or turn it ‘on’ as mentioned here so that you can avoid the message on your screen anytime a new untrusted USB devices is connected to the iPhone or iPad is entirely up to you, and a matter of your own security needs and privacy desires. For some users disabling the alert and USB restriction will be desired, whereas for others they might prefer the sense of security knowing that their device is inaccessible without authorization.

And of course if you turned this feature off so that you’d stop seeing the USB Accessory unlock message, you can always change your mind later, toggling this USB restriction setting off or on as needed in iOS. So perhaps if you’re planning a trip to a place where you’d be more concerned about prying eyes you could return to the default setting of restricting USB accessory access to an iPhone or iPad – it’s your call! If you feel like doing that, simply return to the same settings and turn ‘USB Accessories’ back off again.

This USB security feature exists enabled by default on all iPhone or iPad models running iOS 12 and later, and was first introduced in iOS 11.4.1, but no earlier versions of iOS system software have the USB restrictions as an option, and also won’t display the message when a USB cable is connected to the iOS device.