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Phone number formatter

Clean a list of phone numbers into a uniform international E.164 format.

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Phone number formatter
Paste a list of phone numbers, one per line, and this tool normalizes them into the international E.164 format that SMS gateways, CRMs and messaging APIs expect. It strips spaces, dots, dashes, slashes and parentheses, converts a leading 00 to +, and validates every line — so a messy export mixing 00420 601 123 456 with (415) 555-0123 becomes one clean, uniform column ready to import.
Numbers written in national format with a leading zero need the country prefix option: enter your country code, for example +44, and 020 7946 0958 becomes +442079460958. Without a prefix such lines are marked invalid rather than guessed — the tool never invents a country. The same honesty applies to bare digits with no leading zero or plus: they are only treated as international when you switch that option on. Invalid lines can be removed or kept with a marker so you can fix them by hand, duplicates can be dropped after normalization, and the digits-only output format serves systems that reject the plus sign.
Validation checks the E.164 shape — a plus sign followed by 8 to 15 digits — not whether a number is actually in service or matches a specific country's numbering plan. Treat the result as a formatting pass, not a carrier lookup.
Phone lists are personal data, and that is exactly why this tool runs entirely in your browser. Nothing is uploaded, logged or sent to any server — your customers' numbers never leave your device, which no web service that processes numbers on a backend can promise.
FAQ
Why are numbers starting with 0 invalid when no prefix is set?
A leading zero means national format, and the country cannot be known from the digits alone — 0903 123 456 could be Slovak, Austrian or something else. Set the country prefix and the zero is replaced with it; without one the tool marks the line invalid instead of guessing.
Does the tool check whether a number actually exists?
No. It validates the E.164 shape — a plus sign followed by 8 to 15 digits. It does not check carrier records, whether the number is in service, or country-specific length rules.
Can it merge duplicates written in different styles?
Yes. Turn on "Remove duplicate numbers" and deduplication happens after normalization, so 0903 123 456 with prefix +421 and +421 903 123 456 count as the same number.
What is the digits-only format for?
Some SMS platforms and legacy systems reject the plus sign. The digits-only option outputs 421903123456 instead of +421903123456 while keeping the same validation.
Are my phone numbers uploaded anywhere?
No. The tool runs entirely in your browser and the list never leaves your device. Phone numbers are personal data, so keeping them local is the whole point.