How the lookup works
We read the public central office code and thousands-block reports that the North American Numbering Plan Administrator publishes. A US number is split into its area code, exchange and block, and we look up who received that block.
No call or message is sent, so the person who owns the number never sees the lookup.
Reading the result
The carrier shown is the one the block was first assigned to. Blocks are often handed out in groups of one thousand numbers, so the carrier of the block can differ from the holder of the whole code. Both are shown.
The line type is a hint taken from words in the carrier name, such as wireless. It is not an official category.
Number porting is not reflected. A number that moved to another carrier still shows the carrier of its original block, and the result says that porting is not known.
Limits worth knowing
This is assignment data, not live routing data. It cannot tell you who serves the number today, whether it is active, or whether it has been ported.
Only numbers in the US numbering plan are covered. Canadian and other international numbers return a clear answer saying so.
Frequently asked questions
Is this the carrier I would be billed by?
Not necessarily. It is the carrier the number block was first assigned to. People change carriers and keep their numbers.
Why are two companies listed?
When a central office code is pooled, the holder of the code hands out smaller blocks to other carriers. The block carrier is the one that received your number.
Can it tell me if a number is a mobile line?
Only as a hint from the carrier name. For a numbering plan type, use the phone validator.
Does it work for numbers outside the US?
No. The records cover the US numbering plan only.