Quick Answer
On iPhone, open Settings, tap Phone, scroll to Silence Unknown Callers, and switch it on. Any number that is not in your Contacts, recent outgoing calls, or Mail will go straight to voicemail without making a sound.
On Pixel and most Android phones, open the Phone app, tap the three dot menu, choose Settings, then Caller ID and spam, and turn on both See caller and spam ID and Filter spam calls. On Samsung you do the same thing through the Phone app under Settings, Block numbers, with Block unknown or private numbers switched on.
Why unknown callers are worth blocking
Roughly half the calls hitting a typical mobile number in 2026 are robocalls, spoofed numbers, or scams. The US Federal Trade Commission reported more than 2.6 million unwanted call complaints in the last full year, and that is just the people who bothered to report. Silencing unknown callers does not delete those calls, it just routes them to voicemail so they never interrupt your day.
Legitimate callers (doctors, schools, delivery drivers) almost always leave a voicemail or send a text. Scammers rarely do. The filter sorts them automatically.
Method 1: iPhone (iOS 18 and newer)
On modern iPhones the setting lives inside the Phone app rather than the Messages app.
- Open Settings.
- Scroll down and tap Apps, then Phone (on iOS 18 and newer it sits under the Apps list; on older versions it is in the main Settings list).
- Scroll to Silence Unknown Callers.
- Toggle it on.
Once it is on, your iPhone uses three signals to decide if a caller is safe: are they in your Contacts, have you called them recently, or has their email address appeared in your Mail. If any are true the call rings normally. If none are true the call is silenced and shows up afterwards in your Recents list with a missed call marker, so you can call back if you want.
If you are waiting on a call from an unknown number (a job interview, a tradesperson, a delivery), turn the setting off for the day, take the call, then turn it back on. There is no per contact override.
Method 2: Pixel and stock Android
Pixel phones use a cloud database from Google to identify spam in real time, which means it blocks numbers other people have already flagged.
- Open the Phone app.
- Tap the three dots in the top right, then Settings.
- Tap Caller ID and spam.
- Turn on See caller and spam ID, and Filter spam calls.
For a stricter filter, go back to the Settings list and tap Blocked numbers, then turn on Unknown. That will hard drop any call from a number with no caller ID at all.
If you want Google to screen calls for you live, look for Call Screen on the same Settings page. It answers unknown calls with a virtual assistant, shows you a transcript in real time, and you decide whether to pick up.
Method 3: Samsung Galaxy
Samsung uses its own dialer with two layers of protection. Open the Phone app, tap the three dot menu, then Settings. Tap Block numbers and switch on Block unknown or private numbers. That handles masked and withheld numbers. Then tap Caller ID and spam protection on the same screen and turn it on. Samsung uses Hiya as the database, which flags known telemarketers across millions of phones.
If you would rather keep specific spammers permanently blocked, long press the number in your call log and tap Block.
What about iPhone Focus modes?
Focus modes are a softer alternative. Set up a Focus (Sleep, Work, Personal) and under People allow calls from Favourites or specific contacts. Anyone outside the allow list is silenced for as long as the Focus is on. This is the best option if you do want unknown callers to ring sometimes but never during work or sleep.
Common mistakes
People often turn this on and then panic when a legitimate caller goes missed. Two fixes: save every number you might want to hear from (your kids school, your dentist, the courier company) into Contacts, and check Recents once a day for any unknown number that called more than once, which is usually a sign it was real.
Do not rely on third party blocker apps that demand access to your full contact list. The native iPhone and Android filters are now better, free, and do not sell your data.
The takeaway
Silencing unknown callers is one of the highest impact phone settings you can turn on. iPhone, Pixel, and Samsung all have it built in and it takes under a minute. Combine it with Focus or Do Not Disturb at night and the only calls that interrupt you will be the ones that actually matter.
