Free tools and guides
Phone number formatter and validator
Format phone numbers as E.164, national, or international. Validate pasted numbers or a CSV in your browser. Free, with no signup.
Last reviewed: . Free to use. No signup required.
Format your phone numbers
Paste one number per line, or select a CSV file and its phone column. Choose a default country for national numbers. No account is required.
A leading + country code takes priority. Use the default country only for numbers without one.
Limit: 1 MiB, 10,000 numbers or CSV data rows, and 100 columns. Use UTF-8 CSV with comma separators and a header row.
Your numbers and CSV data stay in this browser. The tool does not upload or save them. Reloading clears the input.
Phone number format examples
These examples show the output before you use the tool. The default country is United States.
| Input | E.164 | National | International | Country | Extension | Result |
|---|---|---|---|---|---|---|
| (415) 555-0101 | +14155550101 | (415) 555-0101 | +1 415 555 0101 | US | — | Valid format |
| +44 20 7946 0018 | +442079460018 | 020 7946 0018 | +44 20 7946 0018 | GB | — | Valid format |
| +1 415 555 0101 ext. 42 | +14155550101 | (415) 555-0101 ext. 42 | +1 415 555 0101 ext. 42 | US | 42 | Valid format |
| not a number | — | — | — | Unknown | — | Invalid |
Use the right format for your import
E.164 uses the country calling code so another system can interpret the number without a default country. A national format is easier to read within its country. An international format adds spaces for readability. An extension remains separate from the E.164 number.
This formatter exports phone results. To keep names, emails, and other CSV columns, use the Attio phone number cleaner.
CSV exports prefix formula-like source cells with an apostrophe. Generated E.164 phone cells contain only a plus sign and digits. Import those files directly into your destination. Spreadsheet apps can remove the plus sign or change digits if they treat a phone column as a number.
Number formats and possible types use the existing libphonenumber-js library. See the ITU E.164 recommendation for the international numbering plan. Numbering plans change; verify important imports in the destination system.
Related tools and guides
Frequently asked questions
What is E.164 phone number format?
E.164 is the international telephone numbering plan. For imports, write a plus sign, country calling code, and national number without spaces. The international number can contain up to 15 digits. Extensions are separate.
Does a valid result mean the phone number is active?
No. Validity means the number fits the library's numbering-plan rules. This tool does not call the number or check ownership, service, consent, or Do Not Call status.
Does my phone number data leave the browser?
No. Pasted numbers and uploaded CSV data are processed in your browser. The tool does not send them to a server or save them. Reloading clears the input.
Which country should I choose?
Choose the country used by numbers without an international country code. A number that starts with + uses its own country calling code. Split a file into country groups if national numbers come from different countries.
Can the tool identify mobile and landline numbers?
It shows a type when the numbering-plan data supports one. Some countries use the same ranges for mobile and fixed lines. The result can be fixed line or mobile, or unknown. It does not establish SMS support.
What happens to extensions and invalid rows?
Extensions appear in a separate result column and in the national and international formats. E.164 does not include them. The results CSV includes every processed row, with invalid rows and their issues clearly marked.
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