What the fax number checker tells you
Every country publishes a numbering plan: which area codes exist, how many digits follow them and which ranges go to landlines, mobiles, toll-free or premium services. The checker compares your number against those plans, so it catches the mistakes that make most faxes fail before they are even dialled: a missing digit, a swapped area code, or a country code typed twice.
- Valid or not: whether the number can exist in that country at all.
- Country and region: for US and Canadian numbers, the state or province of the area code.
- Number type: fixed line, mobile, toll-free or premium rate, where the country's plan says so.
- Formats: the national format as the recipient writes it, and the E.164 format that fax services use.
Why a valid number can still fail as a fax
A valid number is one that can exist, not one with a fax machine on it. Offices often list their main phone number next to the fax number, and the two differ by a digit or two. If a person or a voicemail answers, the fax will not go through. Mobile numbers are the most common trap: outside North America the checker can usually spot them, and you should ask the recipient for a real fax line. In the US and Canada landlines and cell phones share the same area codes, so no tool can tell them apart from the digits alone.
Toll-free numbers (800, 888, 877 and so on) are fine to fax, and many government agencies and insurers use them for inbound faxes. Premium-rate numbers, such as 900 in the US, are rarely fax lines; treat one with suspicion.
How to dial a fax number from the US
Within the US and Canada, dial 1, the three-digit area code and the seven-digit number. For any other country, dial the exit code 011, then the country code, then the number without its leading zero. A Paris number written 01 23 45 67 89 becomes 011 33 1 23 45 67 89. Online fax services skip the exit code: enter the number with a plus, as in +33 1 23 45 67 89, or pick the country and type the rest.
Send the fax once the number checks out
Press Fax this number and the number is filled in on the send page. Add your PDF or a photo of the pages and it is usually delivered in about a minute, with a confirmation when the receiving machine accepts every page. Have paper pages? Use our free phone scanner to turn them into a clean PDF first.
Frequently asked questions
Can this tool tell me if a number is really a fax machine?
No, and no free tool honestly can. A fax line and a phone line use the same numbers. We check the number against the country's numbering plan, which tells you whether it can exist, where it is and what kind of line it usually is. Only calling it tells you whether a fax machine answers.
Can I send a fax to a mobile number?
Almost never. A mobile phone answers with voice, not with a fax tone, so the fax fails after a few attempts. If the checker says a number is mobile, ask the recipient for their fax number. In the US and Canada mobile and landline numbers look alike, so the checker cannot tell them apart.
How do I dial an international fax number from the US?
Dial 011, then the country code, then the number without its leading 0. A London fax number written 020 7123 4567 is dialled 011 44 20 7123 4567 from the US. Online, you can just enter it in E.164 format: +44 20 7123 4567.
What is E.164 format?
The international standard way to write a phone or fax number: a plus sign, the country code and the national number, with no spaces or leading zero, for example +12125551234. Fax services and phone carriers use it to route calls unambiguously.
Is the number I check sent anywhere?
No. The check runs entirely in your browser using the public numbering-plan data in the libphonenumber library. Nothing you type reaches our servers unless you choose to send a fax.
Which countries can Faxio send faxes to?
The US and Canada plus 60 other countries, including the UK, Germany, France, Australia and Japan. The checker tells you for each number whether Faxio can fax it.