Paste a phone number with its country code to see which country it belongs to.
Shared codes like +1 (USA, Canada) and +7 (Russia, Kazakhstan) cover several countries; the area code decides which.
It matches the longest country code at the start of the number.
Codes like +1 and +7 are shared by more than one country.
No. Everything is worked out in your browser and nothing you type is sent to a server.