Regex to Match US Phone Numbers

This regex validates US phone numbers in multiple common formats. Here is the token-by-token breakdown:

^ — Anchors the match at the start of the string.

(?:+1\s?)? — An optional non-capturing group matching the US country code. It matches a literal '+1' followed by an optional whitespace character. This allows formats like '+1 555-123-4567'.

(?:(?\d{3})?[\s.-]?)? — An optional non-capturing group for the area code. (? matches an optional opening parenthesis. \d{3} matches exactly three digits for the area code. )? matches an optional closing parenthesis. [\s.-]? matches an optional separator (space, dot, or hyphen) after the area code. The entire group is optional to allow seven-digit local numbers.

\d{3} — Matches three digits for the exchange code (the first part of the local number).

[\s.-]? — Matches an optional separator between the exchange code and subscriber number.

\d{4} — Matches four digits for the subscriber number (the last four digits).

$ — Anchors the match at the end of the string.

This pattern accommodates the most common US phone number formats: (555) 123-4567, 555-123-4567, 555.123.4567, 5551234567, and variations with the +1 country code. It is flexible enough for user input validation while still ensuring the correct number of digits.