What the “Trust This Computer” alert on your iPhone means

By , Apr 22, 2016


Occasionally, you will be asked on your iPhone, iPod touch, or iPad whether or not you want to “Trust This Computer” when you attach it to a computer with a USB connection either to charge or sync.

If you have ever wondered why this pop up appears, and what it means, then you’ve come to the right place. In this piece, we’ll discuss the alert and why it appears so you’ll have a greater understanding of what it aims to do.

What is the “Trust This Computer” alert?

The alert is essentially telling you that you’ve connected your device to an unknown computer that it’s never been connected to before.

Apple introduced this feature in iOS as a sort of chain of trust to prevent outside machines (both computers and peripherals) from easily getting access to your data. The owner of the device needs to express a trust for the machine by tapping on the Trust button before iOS will communicate with it. If the Don’t Trust button is tapped, then the device will not communicate with the computer it’s plugged into.

When you trust a machine, a special key is saved on both the machine and the iOS device you are establishing a chain of trust on. If the keys match, iOS allows a secure transfer of information between the machine and the device; but when they don’t match, iOS is designed to keep your information safeguarded.

Apple explains that computers you’ve opted to trust are able to do the following things:

  • Sync content through iTunes, such as music and movies
  • Access photographs and videos on the device
  • Access contacts and other content
  • Create iTunes backups of the device

Before a computer can be trusted, you must first unlock the device with its passcode. This is the first step in security to ensure that only the device’s owner can express permission for the device to be used with the machine. Once in, the user of the device can plug it into a Mac or a PC for the first time and the alert will appear.

The alert will not reappear for machines that have already been trusted, but if you recently chose not to trust a machine, and you unplug and plug the device back in again, the alert will reappear, giving you the option to either Trust or Don’t Trust the computer again. If unused for a period longer than 6 months, you may experience a chain of trust expiration, and the trust will have to be reestablished once again.

How to untrust a computer?

Now that you understand the basics of what the Trust This Computer alert really is, you may be wondering if it’s possible to un-trust a machine. The short answer is yes.

You may want to un-trust a machine for a number of reasons – one of the most important being that your PC may have recently been infected with a virus, and you don’t want that virus doing any harm to the media on your device, which would potentially become passed on to others.

By un-trusting the machine, your device can still charge from the USB port as always, but the machine won’t be able to interact with the data and/or media files stored on it.

On devices that are running iOS 8.0 or later, you can untrust all machines by going to Settings > General > Reset > Reset Location & Privacy.

iOS Settings Reset Location & Privacy

Because this will reset everything, this means that all machines you once trusted will now be erased from the device’s memory, and you’ll have to re-trust them one-by-one as they’re connected. There is unfortunately no way to un-trust only one machine at a time.

What to do if the alert isn’t showing up?

In some rare cases, the Trust This Comptuer alert may not even show up when it’s supposed to. In these situations, your device doesn’t trust the computer so it won’t show up in iTunes, but you’re still not given the option to trust the computer to give it access.

So what do you do? – Here are some of the things you can try:

  • Update iTunes – An outdated version of iTunes can and will cause this problem. It’s a part of Apple’s verification process. Make sure you have the latest version of iTunes by checking here.
  • Reseat the device – In some cases, the USB connection could have failed or malfunctioned. Try unplugging the device and using a different USB port.
  • Try another USB cable – If the Lightning or 30-pin cable is bad, you won’t ever get an alert. Try a known good cable and see if the issue persists. Non MFi Lightning cables are notorious for these issues.
  • Turn everything off and on again – In the unlikely event that a USB port’s driver has failed to initialize, try restarting the computer. It doesn’t hurt to restart the iOS device at the same time. Afterwards, try connecting again.
  • Reset your device’s trust settings –  You can try the step above under Settings > General > Reset > Reset Location & Privacy to see if resetting the device’s trust settings will allow you to finally trust the computer.
  • Reset your device’s network settings – If the above didn’t work, you can also try resetting your network settings from Settings > General > Reset > Reset Network Settings. This can sometimes get things working in a flash too.
  • Worst case scenario: contact Apple – If the trust alert still isn’t coming up, contact Apple for support.

Wrapping up

The Trust This Computer alert is an important step to keeping your data safe from someone who steals your device and wants access to your precious information. Utilize the feature wisely and only trust your own computers.


How many machines do you trust to sync with your iOS device(s)? Share in the comments below!

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  • Scott Curry

    “The alert will not reappear for machines that have already been trusted…” This is absolutely incorrect as until I installed iTunes, it showed up every single time I plugged my iPhone into my work computer…

    • That sounds like a bug to me…. a machine that has been trusted shouldn’t ask you repeatedly to trust it again because a key is generated at the time you trust it…

      • iUser2012

        it asks me time to time on same computer without even changing version of iOS or iTunes. I am not sure it is due to JB or chace clearing tweaks but it still asks at least once a week.

      • Scott Curry

        So with other people chiming in…..lots of bugs I guess?

        This has worked perfectly for you every time with every device and every computer?

    • wongnog

      I have the same problem with my work computer. And because they don’t give us admin rights, I CAN’T install iTunes. So every single time I plug in my iPhone (to keep it charging) I get this popup on my phone. So annoying and wish I could get rid of it!!!

    • T_Will

      Same problem here on my work computer.

  • ElzoRillo

    It’s NOT just for unknown computers! I have connected the same iPhone to the same Mac for 4 years and still the alert pops up at least once a week!

  • hkgsulphate

    Everytime I restart my PC I see this alert….