01 · Definition
What is phone number validator?
A phone number validator checks whether a phone number string is syntactically valid for any country, normalises it to E.164 format — the international standard used by SMS carriers and APIs — and identifies the country and dialling code it belongs to. E.164 format is + followed by the country code and subscriber number, with no spaces or dashes.
This tool accepts any number with or without country code, spaces, dashes or brackets, and returns whether it is valid, the E.164 formatted version and the ISO country code. Read the in-depth phone number validator guide for common format errors, country code reference and how to use this validator before loading contacts into an SMS platform.
02 · Process
How it works
- 1Enter the phone number.Type any phone number — with or without the country code, spaces, dashes or brackets. The tool normalises formatting before checking.
- 2Parse against E.164 rules.The validator checks whether the number, once formatted, matches the valid length and prefix pattern for the identified country.
- 3Identify the country.If the number is valid, the tool returns the ISO 3166-1 alpha-2 and alpha-3 country codes and the international dialling prefix.
- 4Return the E.164 formatted number.Valid numbers are returned in E.164 format — the international standard used by SMS APIs, marketing platforms and carrier routing.
03 · Risk
Why it matters
An invalid phone number in an SMS list produces a hard failure — the message is never delivered and most platforms count it against your deliverability rate. Unlike email addresses, phone numbers have strict country-specific length and prefix rules that vary significantly. A syntax check before upload catches these before they reach the carrier.
E.164 format is the universal standard that SMS carriers, marketing platforms and telephony APIs all expect. A number a user typed as '(415) 555-2671' may look correct but fail to deliver because the platform requires '+14155552671'. Validating and normalising to E.164 at the point of collection eliminates this class of failure entirely.
04 · Use cases
Common ways to use this tool
- SMS list hygiene before upload. Validate phone numbers before importing a contact list into an SMS marketing platform to prevent delivery failures and deliverability rate penalties.
- Form input validation. Check that a phone number a user typed on a signup form is syntactically valid and normalise it to E.164 before storing it in your database.
- CRM data cleaning. Audit existing CRM records for invalid phone formats before launching an SMS campaign or migrating to a new platform.
- International number verification. Confirm that a phone number from an international lead has a valid country code and matches the length rules for that country.
- API integration pre-check. Verify that numbers are E.164-formatted before passing them to an SMS API or telephony platform that requires the format strictly.
05 · Interpretation
What to check in the result
- Number returned as invalid with no country data. The number does not match any known country's length or prefix rules. Add the correct country code prefix (e.g. '+1' for US/Canada, '+44' for UK) and re-check.
- E.164 output differs from the input. The validator normalised a locally formatted number to international format — this is correct behaviour. Use the E.164 output when storing or sending, not the original input.
- Valid number but unexpected country shown. If the country code is missing or ambiguous, the validator may assign the wrong country. Always include the full international dialling prefix to ensure accurate country detection.
- Number with letters or special characters. Phone numbers may only contain digits, the leading +, spaces, dashes and brackets. Remove any letters or other characters before checking.
- Short number validates as invalid. SMS shortcodes (5–6 digit numbers used for two-way messaging) are not standard E.164 numbers and will return invalid. They are handled separately by carriers.