The general pattern is: exit code (or +), then the country code, then the number with its domestic prefix adjusted. The catch is the adjustment differs by country — most drop a leading 0, Italy keeps it, Russia drops an 8. This tool applies the right rule for you: pick both countries, paste the number as you see it, and dial the sequence it returns.

+886 is Taiwan's country code. Paste any caller ID into the identify mode to check which country a code belongs to — note that some codes, like +1, are shared by many countries, and the code says nothing about where the caller physically is.

They do the same job — telling the network you're dialing abroad. Exit codes are country-specific (00 in most of Europe and Asia, 011 in North America, 010 in Japan), and some countries offer several through different carriers. + is the universal shorthand that works on any mobile phone worldwide, so on mobiles it's simplest to always use +.

In most countries the leading 0 is a domestic trunk prefix — a signal meaning "long-distance call within this country". Once you dial in from abroad with the country code, that signal is redundant, so it's removed. It is not part of the phone number itself, which is why 02-1234-5678 in Taiwan becomes +886 2 1234 5678.

Italy is the best-known case: for Italian landlines the 0 is part of the number, so +39 06... is correct with the zero. Some countries use a different prefix altogether (Hungary 06, Russia 8), and others have none. This is exactly the kind of exception the tool has built in — and where it isn't verified yet, it says so instead of guessing.

The destination number is the same; only the exit differs. On a mobile you can always start with +, which works worldwide. On a landline there is no + key sequence, so you dial your country's exit code instead (00, 011, 002 and so on). That's why this tool shows both forms whenever your country has a fixed exit code.