What the prefix reader shows
Enter a US or Canadian style phone number in the box above, with or without punctuation and with or without the leading 1. The reader splits the digits into the area code, the exchange and the line number, gives you the international version to save in a contact, and then tells you what it knows about the area code. For a regular US code that means the main places it covers and its time zone. For other codes it names the country or kind of service, such as toll-free or a Caribbean nation. Notes appear underneath when something about the number is unusual.
What it does not know
The reader does not know who owns the number. It does not know the carrier, whether the line is a mobile, a landline or an internet line, and it has no memory of complaints about the number. Those facts sit in private records or in the guesswork of spam-labelling apps, and a tool that claims them from ten digits is selling you something. Our reader is the opposite: small, and honest about its limits. Nothing you type is stored in a database, although the web server's logs keep requests for about a week.
How to read each field
- International form
- The number in the +1 format, which is the one to save in your contacts. It works from any country, because a phone replaces the plus with the right exit code.
- Area code
- The first three digits. They record where the number was first issued, not where the caller is today. The guide on why numbers start with +1 explains why the code after it matters less than people think.
- Exchange and line
- The next three digits and the last four. They rarely tell you anything useful on their own, but a few patterns are flagged: a service-code exchange like 411, repeated digits, or the 555 block that mostly belongs to films.
- Country
- The part that surprises people. A +1 number may be in the US, Canada, a US territory or a Caribbean country. The note beside it says which one, and it affects what a call back may cost.
- Region and time zone
- Shown when the code is a geographic US one. The time zone helps with one simple test: a call at 3 a.m. local time from a code in the opposite zone is more likely to be automated than personal.
Common situations
If the missed call came from a code you do not recognise and left no voicemail, run it through the reader and look at the country first. A Caribbean or foreign result means a return call may be billed at international rates, so wait for a message. The article on calling Canada and the Caribbean goes through that case in detail.
If the result says toll-free, the number has no home city, and anyone can rent such a line, honest or not. If it says 900, the line charges by the call or by the minute, and you should never return a call to it, which is covered in 900 numbers and pay-per-call prefixes. If the reader says it cannot find the area code, the code may be new or unassigned, or the number is not North American, and the guide to +1 and country calling codes helps you tell which.
What to do next
The reader is a starting point and not an answer. When you are unsure about a call, follow these steps in order: do not call back an unknown number; if the caller claimed to be a company, find that company's number on its own website and call that; let unknown numbers go to voicemail, since a real caller leaves a message; and report junk calls at reportfraud.ftc.gov. On an iPhone, Settings > Phone > Silence Unknown Callers will keep strangers from ringing. On Android with the Google Phone app, open Phone, then the three-dot menu, then Settings, and look under Blocked numbers and Caller ID and spam. Registering at donotcall.gov or 1-888-382-1222 stops legitimate telemarketers, but not scammers, so do not expect miracles from it.