Data Sources
Last reviewed: September 16, 2026
All numbering data on this site derives from official public sources — what our Editorial Standards call Tier A sources. This page lists those sources and how often we check each one. For how the data is processed after ingestion, see the Methodology.
Tier A sources
| Source | What we use it for | Our check frequency |
|---|---|---|
| NANPA area code database | Area code (NPA) assignments, statuses, geographic and service designations across the United States, Canada, and Caribbean jurisdictions | Daily |
| NANPA central office (CO) code assignments | NXX code assignments within each NPA, including assignee of record and effective dates | Daily |
| NANPA planning letters | Announced numbering changes: new area codes, overlays, splits, relief planning, and implementation schedules | Event-driven (checked as letters are issued) |
| CNAC (Canadian Numbering Administrator) publications | Canadian numbering resource data and planning materials | Daily |
| FCC reports and public filings | Numbering resource utilization, policy context, and regulatory decisions affecting the NANP | Event-driven (checked as reports are released) |
Each dataset page states the file date of the source data it was built from. "Daily" means we check the source daily; a dataset only changes when the source itself changes.
What we do not use
We do not use the LERG™ (a product of iconectiv) or any other licensed or access-restricted dataset. Our datasets are built exclusively from publicly available official publications. If a data point exists only in a restricted product, we do not publish it.
Attribution and authority
The sources listed above are the authoritative records; our datasets are derived works, and where they disagree with a current official publication, the official publication controls. NumberResearch.org is not affiliated with or endorsed by NANPA, Somos, the FCC, the CRTC, or any regulator — see Ownership & Funding. Attribution requirements for reusing our derived datasets are described in Data Licensing.
Reporting a source issue
If you find a discrepancy between our data and an official source, please tell us: research@numberresearch.org. Discrepancy reports are handled under our Corrections Policy.