Every electronic device you own—your phone, laptop, mouse, keyboard, and every other piece of tech—has a unique serial number. But are those numbers best kept private, like passwords, or is it alright if someone else sees them?

What Is a Serial Number?

A serial number is a unique identifier assigned to a device during the manufacturing process. It’s not necessarily a number—serial numbers can contain letters and symbols as well as numbers. One device’s serial number may look like “123456”, while another device’s may look like “ABC123!@#”. This number may also be identified as a “S/N” on the device..

This unique identifier allows the manufacturer to differentiate between devices that are otherwise completely identical. So, when you need warranty service, a manufacturer can identify that you have a unique device that isn’t a counterfeit and verify it hasn’t already received warranty service.

Manufacturers can use serial numbers to see where a device came from and when it was manufactured, so serial numbers can help identify if there’s a problem somewhere in the manufacturing process. Manufacturers wouldn’t be able to track individual devices without some sort of unique identifier.

Where You’ll Find the Serial Number

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This number is often placed in a sticker somewhere on a device. Turn a device over—whether it’s a laptop, mouse, or keyboard—and there’s a good chance you’ll see a serial number. On a desktop PC, you may see the serial number on the back of the PC, or on a sticker inside the case.  Even if you don’t see a sticker, you’ll often find a serial number printed on the device itself. For example, on Apple’s MacBooks, you’ll see the serial number printed on the bottom next to the “Designed by Apple in California” text.

The serial number is often not printed on smartphones. Instead, it’s available through the software. For example, you’ll find an iPhone’s serial number at Settings > General > About.

You’ll also likely find the serial number on a sticker on the box your device came in.


What Serial Numbers Are Used For

Serial numbers are generally used for warranty service and repairs, but not for much else. For example, if you have an Apple product, you can use a serial number to check whether a device is still within its warranty period and whether you can purchase AppleCare coverage. If you give Apple the serial number, they can trace when you purchased the device. But this isn’t exactly very private information.

RELATED: How to Check the Activation Lock Status of an iOS Device

Apple also allows you to check an iPhone or iPad’s “Activation Lock” status using just its serial number. You can see if the device can be activated, or if it’s locked. This is a security feature that prevents iPhone thieves from wiping and activating phones. Checking is often useful when you’re buying an iPhone or iPad from someone on Craigslist, for example. But this isn’t really sensitive information. All you can see is whether a device is activation-locked or not.

PC, smartphone, and other device manufacturers often offer similar tools, allowing you to check warranty eligibility with a serial number. You can also use a valid serial number to initiate warranty service.

Don’t Be Too Paranoid About Your Serial Numbers

So should these numbers be kept private? After all, they’re unique numbers. If you throw away a box your phone came in and someone grabs it out of your trash, they’ll have your phone’s serial number.

We wouldn’t worry too much about throwing out a box with a serial number on it. You could remove serial numbers from boxes before you throw them away if you like, but the odds that it could cause a problem for you are very low. After all, serial numbers are almost always printed on the device itself. Flip a device over, and you’ll often see a sticker with a serial number. Anyone with physical access to your device could easily glance at it.

Serial numbers are generally visible on the outside of boxes in stores, too. If there was an advantage to knowing serial numbers, people could just head to their local electronics store and record the numbers listed on boxes on the shelf.

If you’re having a device repaired—even by a company that isn’t the manufacturer—that company will often want the device’s serial number so they can look up the exact device you have and the parts it requires. You don’t need to feel squeamish about providing your serial number for repairs. After all, it’s usually printed on the device itself anyway.

Don’t Post Serial Numbers Online, If You Can Help It

It’s unlikely someone would attempt to use a device’s serial number to cause problems for you. A serial number isn’t like a password or credit card number. No one could use a serial number to gain access to your device.

On the other hand, you probably shouldn’t take screenshots or photos of your serial numbers and post them on Instagram or Facebook. It’s just a bad idea to post unique identifiers like that in public. (It’s okay to enter it into the manufacturer’s web site, just don’t post pictures of it anywhere.)

For example, a Lenovo representative has warned against posting the serial number of PCs that are still in warranty because they could be “used to fraudulently order parts [or] file warranty claims”. Some manufacturers may allow you to change your warranty status or other service information with just the serial number, although they really should require more confirmation than that.

Some companies have fairly generous warranty policies that someone with your serial number could exploit. For example, someone may be able to enter the serial number of your mouse into your mouse manufacturer’s website, say it’s broken, and ask for a replacement. If the manufacturer’s warranty policy is generous enough, it may just mail a new mouse to that person, although manufacturers will often ask for a copy of the receipt first. If your mouse breaks in the future and you want to get it fixed, the manufacturer may say your serial number was already used to receive a replacement product.

The odds that someone will use your serial number to fraudulently file a warranty claim are pretty low, but it’s best not to post serial numbers online, just in case.

Image Credit: William Hook/Flickr

Profile Photo for Chris Hoffman Chris Hoffman
Chris Hoffman is Editor-in-Chief of How-To Geek. He's written about technology for over a decade and was a PCWorld columnist for two years. Chris has written for The New York Times and Reader's Digest, been interviewed as a technology expert on TV stations like Miami's NBC 6, and had his work covered by news outlets like the BBC. Since 2011, Chris has written over 2,000 articles that have been read more than one billion times---and that's just here at How-To Geek.
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