# Getting spam calls? See who it is without showing your number, use #31#

> Getting spam calls? Dial #31# before a number to see who it is while keeping your own number hidden. A free, per-call trick for calling back unknown or spam numbers, and it works on most mobile networks.
- **Author**: Nader Cserny
- **Published**: 2026-07-28
- **URL**: https://nader.io/posts/hide-your-number-with-31

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Dialling #31# before a number so the person you call sees "Private Number" instead of your caller ID

The spam calls have been relentless lately. Half the time I want to call a number back just to see who it was, but without handing over my own number in the process, so it doesn't end up on yet another list.

There's a simple trick for exactly this: put **#31#** in front of the number you're dialling and your caller ID is withheld for that one call. So instead of `+420 123 456 789` you dial `#31#+420 123 456 789`, and the other side just sees "Private number" or "Unknown".

## How it works

Type **#31#** immediately before the full number, then hit call. That's it. No settings to change, nothing to remember to switch back on. It applies to that single call only; every other call goes out with your number as normal.

It's a standard network feature (the same one behind your phone's "hide my caller ID" setting), so it works from most mobile phones without any app or setup.

## Why it's handy right now

- **Call back an unknown number** to find out who it was, without giving your own number away.
- **Check who's behind a spam call** while staying anonymous yourself.
- **Keep your number off lists:** callers and their systems can't capture a number they never see.

## The same trick on other networks

`#31#` is the code most mobile networks use, but a couple of regions have their own:

- **Most mobile networks:** `#31#` before the number
- **UK:** `141` before the number
- **US & Canada:** `*67` before the number

If one doesn't take, try another: networks vary, and some show a short confirmation before the call connects.

One thing worth knowing: plenty of people ignore calls from withheld numbers precisely *because* spammers hide behind them. So this is best kept as a per-call trick for calling back the numbers you're curious about, not something to leave on for everyone.

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