In short. From abroad, hiding your number doesn't work the way it does at home. The #31# prefix depends on the visited network and may simply be ignored; your calls and texts go out carrying your number in international +33 format; and many online text-messaging services refuse foreign destinations or charge for them. Anonymity therefore has to be set up before you leave, not from the airport.
Information verified on 19 October 2026 on the public pages of Arcep, the CNIL, the European Commission (roaming regulation), service-public.fr, Légifrance and the public support pages of French mobile operators. This article provides general information and is no substitute for legal advice.
Does the #31# prefix work abroad?
Not reliably. #31# is not a feature of your handset: it is a request sent to the network that routes the call. In France, your own operator handles it. While roaming, it is the visited network that receives the command first, and its behaviour varies from one country and one operator to the next.
Three scenarios occur in practice:
- the visited network interprets the request correctly and the call arrives as a "withheld number";
- the network ignores the prefix, and your full number appears on the recipient's screen;
- the network rejects the call with an error message or a failure tone, because the string you dialled (
#31#++33…) doesn't match a format it accepts.
The detail that trips people up most often: abroad, you have to dial the number in international format. The prefix then goes in front of the entire number, i.e. #31#+33612345678 and not #31#0612345678. Many failures blamed on "the country" actually come down to this simple input error.
If you want reliable withholding, the better approach is the permanent option activated on the operator's side before departure, via your online account or customer service, rather than a prefix typed in case by case. This option is tied to your subscription and therefore follows your line, including when you're latched onto a foreign network. It too remains dependent on the local relay, but it rules out dialling mistakes.
And for a text message: is withholding possible from abroad?
No, no more than in France. A text message necessarily carries an originating address, filled in as it enters the network. #31# acts on voice signalling and has no effect whatsoever on a text message: typing #31# in front of a number before writing a text hides nothing, in France or anywhere else. We explain this in detail in our article on who the sender of an anonymous text is.
From abroad, one nuance is added: your number shows up on the recipient's phone in international format. If you write to a friend or relative in France, their handset will probably display +33 6 12 34 56 78 instead of the usual 06 12 34 56 78. For a contact already saved, the device generally makes the connection. For an unknown number, this international form gives away extra information: it indicates a French line, and sometimes a line being used outside France, depending on what the recipient's operator passes on.
In other words, a text sent from abroad is not "more anonymous". It is merely less legible, which is not the same thing.
Do online text-messaging services work from another country?
Often yes for logging in, less often for sending to a foreign number. Two independent filters come into play.
| What can block it | Why | Practical consequence |
|---|---|---|
| The destination country | Routing to certain countries is expensive or closed off by the wholesale carrier | Sending refused or charged for, even if the service is free to France |
| Your connection IP address | Some services restrict access by country to fight abuse | Page unreachable or an extra verification step required |
| Local regulations | Several countries require bulk message senders to be registered | "Free" alphanumeric sender IDs won't get through |
| The Wi-Fi network used | A hotel or airport Wi-Fi may filter certain sites | A failure that has nothing to do with the service itself |
The most frequently overlooked point is the third one. Several countries, notably in South-East Asia and the Middle East, require business text senders to be declared in advance with the regulator or the operator. A message carrying an unregistered alphanumeric label is simply deleted there. You get no error at all: the message goes out, and never arrives.
What does roaming reveal about you, even with a withheld number?
Far more than the displayed number. The moment your phone latches onto a foreign network, a series of technical details circulates between the visited operator and your French operator: SIM card identifier, device identifier, network used, timestamps. This metadata appears nowhere on your recipient's phone, but it exists in both operators' systems, and can be requisitioned by the courts.
Withholding your number therefore protects you from the recipient's curiosity, never from judicial identification. It's a distinction we spell out in our article on whether an anonymous text is really untraceable, and it counts double abroad, where two operators keep records instead of one.
Add to that what your phone discloses outside the mobile network: successive Wi-Fi connections, Bluetooth identifiers, backup timestamps. An anti-theft travel bag with RFID blocking won't protect you from any of that, but it does at least settle the question of contactless cards and documents while you're in the boarding queue.
How do you set up a discreet channel before leaving?
By testing it at home, while everything still works. The classic mistake is discovering on arrival that your chosen method doesn't get through — with no fallback plan.
- Check the permanent withholding option in your online account (Orange, SFR, Bouygues Telecom and Free Mobile all offer a caller ID setting) and switch it on before you go.
- Test
#31#in international format from France: call a second number by dialling#31#+33…. If it already fails here, it will fail elsewhere. - Create and activate a secondary number before you leave. Almost all secondary-number apps require verification by text at sign-up: if you wait until you're abroad, that verification may fail.
- Write your key numbers down on paper. A hardback notebook tucked into your hand luggage saves you from depending on a phone that's flat or confiscated.
- Plan for battery life. A power bank with a charge display makes all the difference when the only socket is at the far end of the terminal and your flight is delayed.
For the broader business of keeping a reachable channel open in an emergency, our emergency communication plan sets out the fallback logic, which applies as-is when travelling.
Does a local number bought on the spot make you anonymous?
Rarely, and less and less so. Buying a prepaid SIM card abroad is often presented as the ultimate anonymity solution. In reality, the vast majority of countries now require the buyer's identity to be registered at activation: passport presentation, sometimes a photograph, sometimes a fingerprint. The SIM isn't anonymous: it's simply attached to a foreign register rather than a French one.
For a French traveller, that changes four things:
- your number is no longer a +33 one, which blurs the link to your usual identity in the recipient's eyes;
- your ID document is now recorded in a country whose regulations and retention periods you have no control over;
- your French contacts don't know who's getting in touch, which may push your messages into the "unknown" filter on their phone;
- any verification text tied to your usual accounts still arrives on your French line, not the new one.
Data eSIMs, very widespread for some years now, meet a different need: they provide mobile internet, often without a phone number usable for receiving texts. They are therefore not a messaging channel, but they do make a good foundation for encrypted messaging without using the hotel's Wi-Fi.
What does French law say when you send from abroad?
It doesn't put you in the clear. The principle is simple: French law applies as soon as one constituent element of the offence took place in France. If you send a threatening message from Spain to someone living in France, the harm occurs in France, and the French courts have jurisdiction.
The legal classifications are the same as they are inside the country. Harassment, threats and repeated malicious calls are punishable under the Criminal Code; concealing your number is in itself neither an offence nor a mitigating circumstance. The applicable texts can be consulted on Légifrance, and the complaint procedure is described on service-public.fr.
Only one thing genuinely changes: the length of the investigation. Obtaining evidence from a foreign operator goes through international judicial cooperation, which is slower than a domestic request. Slow doesn't mean impossible, and it doesn't protect you — it merely postpones the reckoning. We set out the full framework in our article on the legality of anonymous texts in France.
If you're on the other side of this, i.e. the recipient of an anonymous message received while travelling, the course of action doesn't change: don't reply, keep the original message on the device, and note the timestamp displayed. A multi-port USB mains charger may seem like a trivial detail, but keeping the phone switched on until you get home is precisely what preserves the evidence. Our guide on how to build solid proof details what to save.
What to remember, country by country
There is no universal rule, but three observations hold everywhere:
Withholding your number is a request addressed to a network you don't control. The further you get from your own operator, the less you can guarantee the outcome.
- Within the European Union, roaming is regulated and operator options usually work as they do in France. Call withholding generally gets through; a text message remains identified by your +33 number.
- Outside the European Union, everything depends on the roaming agreement and the visited network. Test a withheld call to a trusted number as soon as you arrive, before you actually need it.
- Everywhere, anonymity towards the recipient and anonymity towards the operators are two separate things. The first is achievable; the second doesn't exist.
For a broader look at discretion while travelling, our readers often go on to read our feature on the travel phone.
Frequently asked questions
Does #31# work everywhere in Europe?
Within the European Union, it works in the vast majority of cases, provided you dial the number in international format (#31#+33…). No operator, however, guarantees its behaviour on every visited network: test it before you need it.
Does my number display differently when I write from abroad?
Yes, usually in international format, i.e. +33 6… instead of 06…. For a contact already saved, the phone generally makes the connection. For an unknown number, the format is simply less familiar.
Can I receive a reply to an anonymous text sent from abroad?
That depends on the method, not the country. Sending via a short code doesn't always allow replies; a secondary number does, provided it was activated and verified before you left. Roaming doesn't change that rule.
Does a local SIM card make me anonymous?
No. Most countries require your identity to be registered at activation. You change register, you don't disappear — and your ID document ends up in a country whose retention rules you don't know.
Does a message sent from abroad escape the French justice system?
No. As soon as one element of the offence occurs in France, notably the harm suffered by the recipient, the French courts have jurisdiction. The investigation is simply slower, because it goes through international cooperation.
Updated 19 October 2026. Network behaviour varies between operators and visited countries: check the caller ID option in your online account before every trip.
