Phone number formatting is more fragile than it looks — here's why
The same phone number can be written a dozen different ways: +1 (415) 555-0123, 14155550123, 415-555-0123, 415.555.0123. All of those represent one number, but a naive string comparison would treat them as six different values. This tool uses Google's libphonenumber library under the hood — the same library Android uses — which means it can parse any of those formats, identify the country from the calling code, and output a single canonical E.164 form: +14155550123. If you're storing phone numbers in a database, E.164 is the right format to normalise to. It's unambiguous, internationalised, and directly usable by SMS and telephony APIs without any further processing.
The distinction between "possible" and "valid" is worth understanding. A possible number has the right length and a plausible prefix for its country — it could theoretically be assigned. A valid number has been cross-checked against the country's actual numbering plan: specific area codes, subscriber number ranges, and number type rules. Validity is the stronger check. The tool also distinguishes mobile from fixed-line where the numbering plan makes that determinable — not all countries do. In the US and Canada the distinction isn't recoverable from the number alone; in the UK a number starting with 07 is almost always mobile. What this tool can't tell you is whether the number is currently active or assigned to a real person — that requires a live carrier lookup via a paid API.