Your Phone Number Is as Important as Your Address
Your phone number is a direct line to you. Just as you would not hand your home address to someone you barely know, your phone number deserves careful handling. Once you have given a number out, you cannot take it back. If the other person takes a screenshot or pastes it into a group chat, it can spread all the way to people you have never met.
When a number gets around, you start seeing sales calls that slip past a nuisance call filter, and friend requests from strangers on social media. Read up on how personal information leaks out from a phone number, and then limit sharing to the people you can honestly say you trust.
Sharing with Friends Is Fine - But Set Yourself Some Rules
There is nothing wrong with giving your phone number to friends you trust. Keep the following rules in mind, though.
Tell Them Directly
Pass your number along in person or in a one-to-one message whenever you can. Posting it in a group chat or on a timeline spreads it to people you never meant to reach. If a group chat has ten members, all ten of them can see your number.
Say "Please Do Not Pass This On"
When you share your number, add a line asking the person not to give it to anyone else. It sounds obvious, but if you never say it, people may assume that passing it along is fine.
Never Put It in a Social Media Profile
Do not, under any circumstances, write your phone number in your Instagram or X (formerly Twitter) profile. That publishes your number somewhere anyone in the world can read it. This is the most basic rule there is for protecting your phone number privacy.
Situations That Call for Extra Care
Someone You Met Online
Handing your phone number to someone you met in an online game or on social media is risky. You have no way of knowing whether they really are a friend your own age. Once they have your number, you may get relentless calls and messages, or find your personal information misused.
With online friends, the safe approach is to stay inside the messaging feature of the service where you met. If you really want to talk by voice, use something like a LINE voice call, which lets you speak without handing over your phone number at all. Our guide for first-time smartphone owners also covers how to deal with callers you do not know.
Prize Draws and Giveaways
Social media campaigns of the "follow and repost to win" variety sometimes ask for your phone number so they can contact the winners. Even when the message appears to come from an official account, think twice before sending your number by direct message. It may well be an impostor account.
Signing Up for Apps and Services
Apps often ask for a phone number when you register. If it is genuinely needed for SMS verification (identity confirmation), you have little choice, but when the field is optional you are safer leaving it blank. If you are registering a number for two-factor authentication, and the service also supports an authenticator app such as Google Authenticator, choosing the app is safer still.
Apps and services based overseas deserve particular care, because Japan's Act on the Protection of Personal Information does not apply to them and how they handle your number can be opaque. Check the terms of service and the privacy policy so that you understand what your phone number will be used for before you sign up.
If Trouble Starts After You Have Shared Your Number
If someone you gave your number to starts calling relentlessly or harassing you, take these steps.
- Add that number to your call blocking list
- Save screenshots and your call history as evidence
- Talk to a parent or guardian
- Talk to a teacher or a school counsellor
- In serious cases, contact the police on #9110
You do not have to put up with it on the grounds that sharing your number was your own mistake. The person doing the harassing is the one in the wrong. Keeping evidence is what makes it possible to act later on.
What to Do When Your Number Has Already Spread
If a number you shared has travelled further than you intended and strangers start calling and messaging, work through the problem in stages.
- Start with call blocking: block calls from unfamiliar numbers one by one. Make use of Silence Unknown Callers on iPhone, or the nuisance call filter on Android
- Work out where the leak came from: think back over who you gave the number to and reason out the route it travelled. If you posted it in a group chat, ask for that message to be deleted
- Review your social media settings: check whether people can find you by searching for your phone number, and turn that off
- Last resort - change the number: if blocking alone cannot keep up, your carrier's shop can change your number for you. There is a fee, but you can normally be on a new number the same day
Changing Your Number as an Option
If the trouble simply will not go away, changing your phone number is a genuine option. Your carrier's shop can handle it, and you can normally have a new number the same day (a fee applies). Once the number changes, give the new one only to people you trust.
When you change numbers, remember to update the number registered with your bank accounts and with every service you use. Services where you have set up SMS verification are the critical ones: leave the old number in place and you may find yourself unable to log in. Drawing up a list before you make the change saves a lot of worry.
Watch Out for LINE's Automatic Friend Adding
LINE has a feature that reads the phone numbers stored in your contacts and automatically adds the LINE accounts behind those numbers as friends. While that feature is switched on, everyone who has your number in their contacts can find your LINE account.
Turning off "Allow others to add me by phone number" in LINE's settings prevents automatic adding by people who know your number. Go to Settings, then Friends, then switch off "Allow others to add me by phone number". If you do want to connect on LINE with someone you gave your number to, adding them by hand with a QR code or a LINE ID is safer.
In Summary
Giving your phone number to friends you trust is fine, but avoid publishing it in group chats or on social media. Do not share it with people you met online. When you do share it, ask the person not to pass it on. And if trouble starts, do not carry it alone - talk to an adult. Those are the basics of managing your number safely. It is worth reading through our detailed advice on managing phone number privacy as well.