What is E.164 format for a phone number?+
E.164 is the ITU-T international numbering plan. Written for machines, a number is a plus sign, the country calling code, and the national significant number with no spaces or punctuation, for example +12025550143. The whole number is at most 15 digits.
Does this validator upload my phone list?+
No. Parsing, normalization, checks, masked evidence, and downloads all happen in the current browser tab. No number is sent to a carrier, lookup service, or csvtodashboard.
Does a valid result mean the number works?+
No. The tool checks structure only. A well-formed number is not proof it is assigned, reachable, or consented for calls or SMS, and no carrier, HLR, or line-type lookup is made.
Why does Excel show my phone numbers as 1.23457E+11?+
The column was stored as a number instead of text. Scientific notation in a saved CSV means digits were rounded away, so the original number must be recovered from the source system, not repaired from the file.
How should extensions be stored?+
Keep the extension out of the main number. The validator moves ext., x, or # extensions into a separate column; in an RFC 3966 tel URI the extension becomes the ;ext= parameter.
What happens to numbers without a + country code?+
You choose a default country. The validator removes that country's national trunk prefix where its rule is known, adds the calling code, and counts how many rows relied on the default.
Why is 555-0100 through 555-0199 flagged?+
NANPA reserves 555-0100 through 555-0199 for fictitious use in entertainment and advertising, so a +1 number in that range is flagged for review rather than treated as a real contact.
Are duplicate numbers removed?+
Exact duplicates after normalization, including the same extension, are blocked from the clean list and kept in the flagged list. The same number with a different extension is a review.