800 Service Management System
Information about the central database for US toll free number management.
Active Numbers Online
OFTEL UK numbering allocations, North American area codes and country codes, with associated tariff information.
Area Code Information
Detailed information on the history and current developments in North American NPA allocations.
International Numbering Plans
A collection of all international numbering plans in the world. Some features require a paid subscription.
Number Portability
Collates information on the regional initiatives in place to develop number portability and number pooling in the US.
The Telephone Exchange Name Project
The historical relationship between North American telephone exchange names and numbers.
World Telephone Numbering Guide
Detailed information and news on public numbering plans from around the world.