NPA-NXX - 303-378

This is the 303-378 subcode (NPA-NXX) prefix page. Follow a prefix to find the number you are looking for. We divide our pages up to make them more user friendly to navigate!

1. Area Codes
2. 303
3. 303-378

The 303-378 subcode mainly covers Denver in Denver county. But other numbers maybe included as well.

We have a database of information derived from the public phone records of Colorado state. Many of the numbers in this subcode are Cellular (Dedicated) registered to At&t Mobility. We hear they employ a large number of people in the Colorado office.
Recently there have been an increase in reported calls, we've had over 600158 comments across our systems for the 303-378 subcode.