Your phone displays "No Caller ID", "Private" or "Unknown" and you wonder who is calling. This situation often causes anxiety: could it be a doctor, an employer, a relative in an emergency — or a canvasser or scammer trying to hide their identity? This guide explains why numbers are masked and what you can do.
Why can a number be masked?
In France, any subscriber can hide their number by dialling #31# before the called number, or by activating the permanent caller ID restriction option (CLIR) with their carrier. Legitimate reasons include doctors, social workers, legal professionals, journalists or harassment victims who regularly use this feature. But canvassers and scammers also use it to avoid being identified and blocked.
Can you identify the caller behind a masked number?
As a private individual, you cannot identify the caller behind a masked number by yourself. Number masking is a legally protected feature. Your carrier knows the caller's identity (it is transmitted through the network but blocked before display), but is not authorised to share it with you. Only a judicial requisition can compel a carrier to lift a caller's anonymity. If you are being harassed via a masked number, file a complaint — the authorities can then legally obtain this information.
Strategies for handling masked calls
- Let it ring without answering: legitimate callers (doctor, employer) generally leave a voicemail or send an SMS. A canvasser or robot hangs up without leaving a message.
- Activate voicemail: set your phone to automatically forward masked calls to voicemail. You can then decide whether to call back after listening to the message.
- Dial 3131: if you did not answer, dialling 3131 immediately after a masked call can sometimes reveal the number if the caller has allowed this unmasking. This service remains limited, however.
- Block masked numbers: on iPhone (iOS 13+), you can activate "Silence Unknown Callers". On Android, some carriers offer a masked number blocking service via the client portal.
Should you answer masked numbers?
There is no universal rule. If you are expecting an important call from a healthcare professional, recruiter or emergency service, it may be worth answering. If you do not generally receive important professional calls on this number, letting it ring and checking voicemail is often the best option. Masked number scams exist (fake police, fake lawyers), but they are less common than visible-number scams because masking reduces the effectiveness of standard manipulation techniques.
Harassment via masked number: your legal recourse
If you are receiving repeated malicious calls from a masked number, you have legal options. File a report or complaint with the police or gendarmerie. Contact your carrier to activate specific protection. In cases of serious threats, the prosecutor's office can order a judicial requisition to lift the anonymity. Keep a call log (time, duration, content) to build a solid case file.