Regex Editor & Tester

Matches either a single digit at the start of a line followed by optional whitespace, or an opening parenthesis at the start of a line. With the multiline flag, the ^ anchor applies at the beginning of every line rather than just the string. This makes it useful for detecting lines that begin like common US phone number formats, such as '555-555-5555' or '(555) 555-5555', and is a typical exercise pattern for phone number validation practice.